Biomedical subjects

Norbert Meier

Publications and source records attributed to Norbert Meier.

10 recordsLinked to original sources

PubMed2006

Assessment of bone marrow angiogenesis in patients with acute myeloid leukemia by using contrast-enhanced MR imaging with clinically approved iron oxides: initial experience.

PURPOSE: To prospectively assess bone marrow (BM) angiogenesis in patients with acute myeloid leukemia (AML) by using iron oxide-enhanced magnetic resonance (MR) imaging. MATERIALS AND METHODS: The study was institutional ethics committee approved. Informed signed consent was obtained from each study participant. The requirement for informed consent for use of data from a reference database was waived. Eleven patients (seven women, four men; mean age, 53 years+/-4.40 [standard deviation]) with an initial diagnosis of AML were enrolled in the study and underwent T2*-weighted two-echo echo-planar MR imaging of the pelvis before and after intravenous injection of a clinically approved iron oxide blood-pool contrast agent. Six healthy control subjects (one woman, five men; mean age, 35 years+/-2.31) were examined with the same MR protocol. The iron oxide-induced change in R2* relaxation rate (DeltaR2*) was calculated, and the vascular volume fraction (VVF) of the BM was derived by dividing the DeltaR2* of the BM by the DeltaR2* of the muscle. Parametric DeltaR2* maps were calculated to visualize vessel distribution. Patients underwent BM biopsy for correlative determination of microvessel density (MVD) and vascular endothelial growth factor (VEGF). Differences in DeltaR2*, VVF, VEGF, and MVD were compared by using the Wilcoxon rank sum test. RESULTS: DeltaR2* maps showed prominent areas of highly vascularized BM in the patients with AML, whereas the control subjects had moderately vascularized BM with homogeneous vessel distribution. Quantitative analysis revealed VVF values to be significantly higher in patients with AML than in control subjects: The mean VVF in the pelvis was 9.18%+/-1.54 for patients versus 3.91%+/-0.61 for control subjects (P=.010). In accordance with MR results, MVD (P=.009) and VEGF expression (P=.017) were significantly elevated in the AML group compared with values in the control group. CONCLUSION: Iron oxide-enhanced MR imaging enables assessment of BM angiogenesis in patients with AML.

Bone Marrow Neoplasms↗

PubMed2006

The position of the aorta relative to the spine before and after anterior instrumentation in right thoracic scoliosis.

STUDY DESIGN: Preoperative magnetic resonance images (MRI) and postoperative axial computed tomography (CT) scans in 25 consecutive patients with idiopathic right thoracic adolescent scoliosis (AIS) and anterior correction and fusion with a dual rod system were analyzed in a prospective study. OBJECTIVES: Evaluation of the spatial relations between the vertebral body and the aorta and the relative migration of the aorta due to the anterior correction and instrumentation in right thoracic scoliosis patients. SUMMARY OF BACKGROUND DATA: In anterior scoliosis surgery, bicortical screw purchase is performed to increase pullout strength. However, impingement of the aorta due to excessive contralateral screw penetration has been reported, especially after endoscopic instrumentation. For a safe screw placement, knowledge of both the preoperative topographic relation of aorta and vertebral body and its changes due to surgical correction is crucial. Recent studies reported on a more lateral and posterior position of the aorta in AIS patients. However, there are hardly any data on the changes of the aortic position after anterior curve correction available in the current literature. METHODS: All 25 patients underwent an identical anterior surgical technique with standard open approach and dual rod instrumentation of the primary curve. Preoperative MRI and postoperative sequential CT scans of 180 vertebrae were analyzed with respect to following parameters: vertebral body width and depth, diameter of the aorta, closest distance between aorta and the vertebral body, the aorta-vertebral angle, and the position of the aorta in relation to the spinal canal. RESULTS: Before surgery, the aorta is positioned posterolaterally with an aorta-vertebral angle of between 78 degrees and 92 degrees (between T5 and T10). Between T11 and L2, the aorta is positioned more anteromedially with an aorta-vertebral angle from 62 degrees (T11) to 16 degrees (L2). After surgery, the aorta has migrated from a posterolateral to a more anteromedial position. This migration is maximal at the apex vertebra with an average change of the aorta-vertebral angle of 31.4 degrees . Whereas the distance between the aorta and the vertebral body increases at the upper and lower fusion levels, the aorta moves significantly closer to the vertebral body at the curve apex due to surgical correction. In patients with thoracic hypokyphosis, the aorta is positioned significantly more posterior than in patients with hyperkyphosis. CONCLUSIONS: This MRI and CT based study of 25 patients with thoracic AIS treated by standard open dual rod and dual screw instrumentation demonstrates a migration of the aorta by 31 degrees from a more posterolateral position before surgery to a more anteromedial position after surgery at the curve apex. Scoliosis surgeons should be aware of these changes; any excessive contralateral screw penetration must be avoided at any level.

Adolescent↗

PubMed2005

Anterior dual rod instrumentation in idiopathic thoracic scoliosis: a computed tomography analysis of screw placement relative to the aorta and the spinal canal.

STUDY DESIGN: Axial computed tomography scans (CT) in 20 consecutive patients with idiopathic right thoracic scoliosis and anterior correction and fusion with a dual rod dual screw system. OBJECTIVES: CT evaluation of screw position in anterior dual rod instrumentation relative to the aorta and the spinal canal. SUMMARY OF BACKGROUND DATA: In anterior scoliosis surgery, bicortical screw purchase is used to increase pullout strength. However, impingement of the aorta due to excessive contralateral screw penetration has been reported, especially after endoscopic instrumentation. Data on the accuracy of dual screw instrumentation in thoracic scoliosis are missing. METHODS: All 20 patients underwent an identical anterior surgical technique with double thoracotomy approach and dual rod instrumentation of the primary curve. Postoperative sequential CT scans were analyzed with respect to following parameters: vertebral body width and depth, diameter of the aorta, distance from the aorta to the closest point of the vertebral body cortex, distance between the tip of the screws and the aorta, distance between the screw and the spinal canal, and the amount of contralateral screw penetration. A total amount of 226 screws were evaluated. RESULTS: All screws were placed correctly without any critical proximity to the aorta or spinal canal. A total of 198 of 226 screws (88%) had a bicortical purchase. Thirteen screw tips (5.8%) were within 1 to 3 mm proximity to the aorta. All other screws were more than 3 mm distant from the aorta. The closest proximity of the screw tips to the thoracic aorta was found at the upper end vertebrae (T5, T6, or T7). There were no screws perforating the spinal canal. CONCLUSION: Anterior instrumentation and correction of thoracic scoliosis with a dual rod dual screw system enable a correct and safe screw placement using a standard open approach. Excessive bicortical screw perforation should be avoided in order not to endanger the thoracic aorta.

Adolescent↗

PubMed2005

CT-based accuracy of implanting custom-made endoprostheses.

BACKGROUND: To optimize physiological load transfer and mechanical stability a close geometric fit between cementless stems and the bone stock is essential. To solve the problem of a geometric mismatch between the anatomic shape of the femoral canal and conventional stems custom-made implants were developed. This study determined the accuracy of implanting custom-made press-fit straight femoral stems compared to conventional cementless stems. METHODS: Nine pairs of human cadaveric femurs were used to determine the extent of the endocortical area in contact with the stem. The bone-femoral component interface was measured in vitro using CT-data analysis. A software program was developed to describe the periprosthetic inner cortical bone structure, the stem surface and the proportionate implant-endosteal bone contact. FINDINGS: The mean endosteal bone contact of both prostheses was 21.6%. The proportionate implant-endosteal bone contact for straight custom-made femoral prostheses averaged 20.98%. For the conventional cementless stems the mean proportionate contact was 22.15%. Especially in the proximal femur the desirable contact of customized implants was not achieved by closed distal press-fit. INTERPRETATION: Compared to conventional straight cementless stems custom-made stems did not extend the endocortical contact area. The desirable "fit and fill" of the proximal femur was not achieved with straight custom-made femoral components in femurs of regular geometry.

Adult↗

PubMed2003

CT colonography: Protocol optimization with multi-detector row CT--study in an anthropomorphic colon phantom.

PURPOSE: To determine optimal detector collimation, section thickness, and tube current for multi-detector row computed tomography (CT) colonography. MATERIALS AND METHODS: An anthropomorphic colon phantom with simulated polyps of varying size (2, 6, 8, 10, and 12 mm) was examined by using multi-detector row CT with varying combinations of detector collimation (4 x 1.0 mm and 4 x 2.5 mm), dose per section (10, 20, 40, 60, 80, 100, and 140 mAs), and section thickness/reconstruction interval (1.25/0.6, 2.0/1.0, 3.0/1.0, and 5.0/2.0 mm). Polyp depiction, longitudinal polyp distortion, and presence of rippling artifacts were assessed on reformatted three-dimensional endoluminal images by three reviewers. RESULTS: Longitudinal distortion and rippling artifacts increased with increasing section thickness and use of broader detector collimation. Polyps 8 mm or larger were depicted with any combination of section thickness, detector collimation, and tube current. Depiction of polyps 6 mm or smaller depended on the detector collimation/reconstructed section thickness and was rated optimal for the 4 x 1.0-mm detector collimation with a section thickness of 1.25 mm. This was also observed for low-dose protocols. Polyps 6 mm or smaller that were not detected with 3-mm section thickness and 4 x 2.5-mm detector collimation were detected with 1.25-mm section thickness and 10 mAs. CONCLUSION: A narrow detector collimation with thin-section imaging (4 x 1.0-mm detector collimation, 1.25-mm section thickness) is a prerequisite for low-dose (10-mAs) multi-detector row CT colonography.

Artifacts↗

PubMed2002

Public domain computer-aided surgery (CAS) in orthodontic and maxillofacial surgery.

BACKGROUND: Computer-aided virtual three-dimensional (3D) surgical simulation assists the necessary visual understanding of complex pathological situations but has so far been dependent on expensive hardware and software. METHOD: For the first time a non-commercial, user-orientated application for orthognathic and craniofacial surgical simulation has been introduced, based on freeware NIH Image 1.62 provided by the National Institute of Mental Health (NIMH). Use and limitations are demonstrated here by the example of hypertelorism surgery. The osteotomy lines and the amount of resection for outward positioning of the orbits were determined by the surgeon on a workstation using CT data. Possible movement patterns of the osteotomy fragments were rotations, sagittal and transversal movements or combinations of these. The program then allows the calculation of anatomical distances on the screen in a 1:1 relation. Normative values according to age and pathological anatomy determine the degree of displacement. The program calculates the new position of the osteotomy fragments and transfers the data of the segment movement to the original CT data. RESULTS: 3D visualization of bone and soft tissue contours have been produced with an acceptable quality on a workstation for the demonstration and visual understanding of the surgical plan. Evaluation of a postoperative CT showed that the amount of movement and size of bone resection in the simulation was slightly overestimated rather than underestimated. This was also dependent on the complexity of the pathological anatomy and on how experienced the surgeon was. CONCLUSION: The use of 3D simulation programs allows a better understanding of the pathological anatomy in all dimensions, and in many cases enables limitations to be recognized in advance. The public domain program makes a major contribution to the quality of orthognathic and craniofacial surgical planning through cost-free usability, and supports continuous development and exchange of experience.

Cephalometry↗

PubMed2002

Local differences in the trabecular bone structure of the proximal femur depicted with high-spatial-resolution MR imaging and multisection CT.

RATIONALE AND OBJECTIVES: The authors performed this study to investigate structural variations in the trabecular bone of the proximal femur at high-resolution magnetic resonance (MR) imaging and high-resolution multisection computed tomography (CT). MATERIALS AND METHODS: Bone mineral density (BMD) was measured in 36 proximal human femur specimens by using dual x-ray absorptiometry. High-resolution MR imaging was performed at 1.5 T with an in-plane spatial resolution of 0.195 x 0.195 mm and a section thickness of 0.3 and 0.9 mm. Multisection CT was performed with an ultra-high-resolution protocol; images were obtained with an in-plane spatial resolution of 0.25 mm and a section thickness of 1 mm. In a subset of these specimens, micro CT was performed with an isotropic spatial resolution of 30 microm. Identical regions of interest (ROIs) were used to analyze images obtained with MR imaging, multisection CT, and micro CT. Trabecular bone structural parameters were obtained, and the parameters from the individual imaging modalities and BMD were correlated. RESULTS: Significant differences concerning the trabecular microarchitecture between the individual ROIs were demonstrated with multisection CT and MR imaging. A number of the correlations between structural parameters derived with multisection CT, MR imaging, micro CT, and BMD measurements were significant. For MR imaging, threshold technique and section thickness had an effect on structural parameters. CONCLUSION: Structural parameters obtained in the proximal femur with multisection CT and high-resolution MR imaging show regional differences. These techniques may be useful for depicting the trabecular architecture in the diagnosis of osteoporosis.

Adult↗

PubMed2002

Optimizing presurgical orthodontic planning by means of the transverse coordinate simulation system (TCSS).

INTRODUCTION: When planning bilateral sagittal split osteotomies according to Obwegeser and Dal Pont, inaccuracies in the presurgical prediction of the transverse osteotomy gaps may occur. This is due to limitations of plaster models when simulating surgery on an articulator. AIM: This paper demonstrates the transverse coordinate simulation system which allows presurgical prediction of the transverse discrepancy between the tooth bearing and the proximal segment after displacement, thus minimizing uncertainty for the surgeon. METHOD: Diagnostic landmarks (taken from lateral and frontal cephalograms) and clinical data describing mandibular dimensions are transferred to a two-dimensional coordinate diagram. A mandibular model is then constructed using the anterior arch form, the temporomandibular joint distance and the prospective incision pattern. RESULT: Movements in the horizontal plane and displacement of the three segments (two condylar and one mandibular arch segment) can be simulated and measured. CONCLUSION: Transverse coordinate simulation system effectively increases the accuracy of presurgical planning without additional CT data or three-dimensional jaw models. This technique may decrease the number of additional surgical manoeuvres resulting from unexpectedly wide transverse discrepancies at the osteotomy site, which often increase surgery time, necessitate additional bone grafting, and entail the risk of healing disturbances and of malrotation or dislocation of the condyle.

Cephalometry↗

PubMedDate not supplied

[Antibody titer against bovine viral diarrhea virus (BVDV) in bulk milk samples from Bavaria].

A total of 5204 bulk milk samples were tested for antibodies against bovine viral diarrhea virus (BVDV) classified according to the scheme after Alenius. Forty-five percent of the samples from 2002 were classified as class 0 and class 1, 55% as class 2 and 3. 6420 bulk milk samples from 1997 were classified in an independent study in 65.6% class 0 and 1 and 34.4% in class 2 and 3. In class 0 and class 1 farms only very rarely persistent viremic animals have been found, whereas in class 2 and 3 their presence is highly likely. Our studies with non-selected sera defined the serological screening of bulk milk samples as a promising tool for a possible BVDV eradication program in Bavaria.

Animals↗

PubMedDate not supplied

[Feasibility of serological bulk milk testing as a method for BVD surveillance].

A commercial ELISA detecting antibodies against bovine viral diarrhoea Virus (BVDV) was analysed for its applicability for bulk-milk screening. Detection limits were analysed using native and concentrated milk samples (milk treated with rennet and ammonium sulfate precipitated) from 10 cows whose sera showed different reactivity levels in the ELISA and from two cows which gave birth to persistently infected calves during the last year. Further this and a second commercial ELISA were used to screen 591 randomly selected bulk-milk samples. To clarify discrepancies thirty-nine herds were included in a follow-up study. A second bulk-milk sample and serum samples from 10 young cattle of 6 to 28 month of age per herd were analysed for antibodies against BVDV. The results of this second testing and the detection of viremic animals in 4 herds confirmed the results from initial bulk-milk testing with both tests. The analysed test is suitable for bulk-milk testing although its application is limited by vaccination.

Aging↗