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T Stammberger

Publications and source records attributed to T Stammberger.

At least 19 recordsLinked to original sources
PubMed2002

Quantitative image analysis of the cartilage in Virtual Reality.

The objective of this work is to develop image processing methods for analysing the morphology of the joint cartilage with magnetic resonance imaging. Quantitative data on the morphological distribution of the joint cartilage are of great interest for both research as well as for diagnosis. The cartilage thickness provides information on the local cartilage occurance and may therefore be helpful in early and objective diagnosing degenerative cartilage changes, monitoring the pathogenesis of osteoarthritis, and controlling the success of chondroprotective treatment. In biomechanics, the thickness distribution serves to analyse the functional adaptation or the compression of the cartilage under loading and may be used for numerical simulation of load transmission in the joint.

Biomechanical Phenomena↗
PubMed2001

[Effect of muscle activity on the 3-dimensional movement pattern of the shoulder. Study with open MRI].

The objective of this study was to analyze the influence of shoulder muscle activity on the three-dimensional motion pattern of the shoulder girdle in the living. 14 healthy volunteers were investigated with an open MRI system at 60-120 degrees abduction--with and without activity of the shoulder abductors. The 3D motion pattern of the humerus, scapula, clavicle and M. supraspinatus were computed. Under muscle activity, the glenoid demonstrated a slightly reduced elevation at 60 degrees of abduction (20.5 degrees +/- 8.2 degrees vs. 23.1 degrees +/- 6.3 degrees; not significant), and at 120 degrees a significantly higher degree of rotation under muscle activity (43.3 degrees +/- 8.6 degrees vs. 36.1 degrees +/- 5.2 degrees; p < 0.01), whereas at 90 degrees no difference was observed. This caused a significant reduction of the scapulo-humeral rhythm at 120 degrees (2.6 vs. 1.5; p < 0.01), a significant increase of the supraspinatus angle (123.3 degrees +/- 6.7 degrees vs. 117.3 degrees +/- 6.5 degrees; p < 0.05) as well as a reduction of the supraspinato-humeral relationship (1.0 vs. 0.97). The study demonstrates that muscle activity leads to an alteration of shoulder girlde motion patterns at higher degrees of abduction, with increased rotation of the scapula, an altered spatial relationship between the supraspinatus and humerus.

Adult↗
PubMed2001

Optimization and validation of a rapid high-resolution T1-w 3D FLASH water excitation MRI sequence for the quantitative assessment of articular cartilage volume and thickness.

In view of follow up, survey and development of therapeutic strategies for osteoarthritis where cartilage deterioration plays an important role, a non invasive, reliable and quantitative assessment of the articular cartilage is desirable. The currently available high resolution T(1)-weighted (T1-w) 3D FLASH pulse sequences with frequency selective fat suppression are very time consuming. We have 1) optimized a high resolution T1-w 3D FLASH water excitation (WE) sequence for short acquisition time and cartilage visualization, and 2) validated this sequence for cartilage volume and thickness quantification. The spectral fat presaturation was replaced by selective water excitation. The flip angle of the WE sequence was optimized for the contrast to noise (C/N(cart)) ratio of cartilage. Sagittal datasets (voxel size: 0.31 x 0.31 x 2 mm(3)) of the knees of nine healthy volunteers were acquired both, with the 3D FLASH WE (17.2/6.6/30 degrees ) sequence (WE) and a previously validated 3D FLASH fat saturated (42/11/30 degrees ) sequence (FS). For validation of the WE sequence, cartilage volume, mean and maximal cartilage thickness of the two sequences were compared. Reproducibility was assessed by calculating the coefficient of variation (COV %) of 4 consecutive WE data sets in the volunteers. The acquisition time was reduced from 16'30" (FS) down to 7'14" for the WE sequence. Image contrast and visualization of the cartilage was very similar, but delineation of the basal layer of the cartilage was slightly improved with the WE sequence. A flip angle of 30 degrees provided the best C/N(cart) ratios (WE). Reproducibility (COV) was between 1.9 and 5.9%. Cartilage volume and thickness agreed within 4% between FS and WE sequence. The WE sequence allows for rapid, valid and reproducible quantification of articular cartilage volume and thickness, prerequisites for follow-up examinations. The reduced acquisition time (50% of FS) enables routine clinical application and thus may contribute to a broader assessment of osteoarthritis.

Adult↗
PubMed2001

Three-dimensional analysis of shoulder girdle and supraspinatus motion patterns in patients with impingement syndrome.

Alterations of the shoulder girdle motion have been suggested to be associated with shoulder disorders. The objective of this study was to perform a three-dimensional (3D) motion analysis of the supraspinatus muscle and shoulder girdle in patients with different stages of impingement syndrome. 20 patients with unilateral impingement and 14 normal controls were investigated at 30 degrees, 90 degrees, and 120 degrees of abduction with and without abducting muscle activity. The spatial relationship between the shoulder girdle elements and the supraspinatus was quantified from open MRI data. No significant alterations in glenoid rotation were observed between the patients and asymptomatic volunteers. However, while in the healthy volunteers the values showed a normal distribution (28.5+/-3.6 degrees at 90 degrees abduction with muscle activity), the patients (30.5 degrees+/-9.7 degrees) contained a subset of five individuals with an obvious increase in glenoid rotation angle (>40 degrees) compared with controls (>2.5 standard deviations higher than the mean) and with the healthy contralateral side. These five patients also displayed alterations in the scapulo-humeral rhythm and supraspinatus motion, but not in clavicular position. The study shows that only a specific subset of patients with impingement syndrome demonstrates complex changes in shoulder girdle and supraspinatus motion patterns, suggesting that this subset may benefit from an alternative type of treatment.

Adult↗
PubMed2000

Effect of gradient and section orientation on quantitative analysis of knee joint cartilage.

The object of this study was to determine the influence of the gradient and section orientation on cartilage thickness and volume measurements in the knee joint. Eight specimens were imaged with a fat-suppressed gradient-echo sequence, applying sagittal, transverse, and coronal section orientations. Images were additionally acquired with exchanged gradient directions, and with computed tomography (CT) arthrography. After segmentation and three-dimensional (3D) reconstruction, the volume, the mean, and the maximal 3D cartilage thickness were computed. No effect of changes in the gradient orientation was found, suggesting that susceptibility-induced geometric distortion is not a relevant problem in quantitative cartilage imaging. Sagittal images produced similar data to that obtained with transverse (patella) or coronal (tibia) sections, demonstrating that all knee joint cartilages can be accurately quantified from a single sagittal data set. Whereas no significant systematic deviation between magnetic resonance imaging (MRI) and CT arthrography was recorded in the patella, there was a 10%-15% underestimation of tibial cartilage thickness in MRI.

Cartilage, Articular↗
PubMed2000

Elastic registration of 3D cartilage surfaces from MR image data for detecting local changes in cartilage thickness.

The objective of this work was to develop and validate a computational method for the registration (matching) of 3D cartilage plates from MR image data sets. The technique tracks local cartilage thickness changes over time. A 3D elastic registration technique was applied that identifies corresponding points of the bone-cartilage interface in MR data sets of 3D-reconstructed cartilage plates. In a first rigid preregistration step, the surfaces are aligned, using the principal axes decomposition to correct for different joint positions and orientations in the MR scanner. In a second step, the surfaces are deformed elastically, based on geometric surface features, until they are sufficiently similar to identify corresponding surface points. The method was validated against artificially corrupted cartilage surfaces and MR data obtained from in vivo and in vitro compression experiments. The in vivo reproducibility was tested on patellar data sets of volunteers, with repositioning of the joint in between replicate acquisitions.

Cartilage, Articular↗
PubMed2000

Precision of tibial cartilage morphometry with a coronal water-excitation MR sequence.

The aim of this study was to analyze the precision of tibial cartilage morphometry, by using a fast, coronal water-excitation sequence with high spatial resolution, to compare the reproducibility of 3D thickness vs volume estimates, and to test the technique in patients with severe osteoarthritis. The tibiae of 8 healthy volunteers and 3 patients selected for total knee arthroplasty were imaged repeatedly with a water-excitation sequence (image time 6 h 19 min, resolution 1.2 x 0.31 x 0.31 mm(3)), with the knee being repositioned between each replicate acquisition. After 3D reconstruction, the cartilage volume, the mean, and the maximal tibial cartilage thickness were determined by 3D Euclidean distance transformation. In the volunteers, the precision of the volume measurements was 2.3 % (CV%) in the medial and 2.6 % in the lateral tibia. The reproducibility of the mean cartilage thickness was similar (2.6 and 2.5 %, respectively), and that of the maximal thickness lower (6.5 and 4.4 %). The patients showed a considerable reduction in volume and thickness, the precision being comparable with that in the volunteers. We find that, using a new imaging protocol and computational algorithm, it is possible to determine tibial cartilage morphometry with high precision in healthy individuals as well as in patients with osteoarthritis.

Adult↗
PubMed2000

Patellar cartilage deformation in vivo after static versus dynamic loading.

The objective of this study was to test the hypothesis that static loading (squatting at a 90 degrees angle) and dynamic loading (30 deep knee bends) cause different extents and patterns of patellar cartilage deformation in vivo. The two activities were selected because they imply different types of joint loading and reflect a realistic and appropriate range of strenuous activity. Twelve healthy volunteers were examined and the volume and thickness of the patellar cartilage determined before and from 90 to 320s after loading, using a water excitation gradient echo MR sequence and a three-dimensional (3D) distance transformation algorithm. Following knee bends, we observed a residual reduction of the patellar cartilage volume (-5.9+/-2.1%; p<0.01) and of the maximal cartilage thickness (-2.8+/-2.6%), the maximal deformation occurring in the superior lateral and the medial patellar facet. Following squatting, the change of patellar cartilage volume was -4.7+/-1.6% (p<0.01) and that of the maximal cartilage thickness -4.9+/-1.4% (p<0.01), the maximal deformation being recorded in the central aspect of the lateral patellar facet. The volume changes were significantly lower after squatting than after knee bends (p<0.05), but the maximal thickness changes higher (p<0.05). The results obtained in this study can serve to validate computer models of joint load transfer, to guide experiments on the mechanical regulation of chondrocyte biosynthesis, and to estimate the magnitude of deformation to be encountered by tissue-engineered cartilage within its target environment.

Adult↗
PubMed2000

Glenohumeral translation during active and passive elevation of the shoulder - a 3D open-MRI study.

Despite its importance for the understanding of joint mechanics in healthy subjects and patients, there has been no three-dimensional (3D) in vivo data on the translation of the humeral head relative to the glenoid during abduction under controlled mechanical loading. The objective was therefore to analyze humeral head translation during passive and active elevation by applying an open MR technique and 3D digital postprocessing methods. Fifteen healthy volunteers were examined with an open MR system at different abduction positions under muscular relaxation (30-150 degrees of abduction) and during activity of shoulder muscles (60-120 degrees ). After segmentation and 3D reconstruction, the center of mass of the glenoid and the midpoint of the humeral head were determined and their relative position calculated. During passive elevation, the humeral head translated inferiorly from +1.58mm at 30 degrees to +0. 36mm at 150 degrees of abduction, and posteriorly from +1.55mm at 30 degrees to -0.07mm at 150 degrees of abduction. Muscular activity brought about significant changes in glenohumeral translation, the humeral head being in a more inferior position and more centered, particularly at 90 and 120 degrees of abduction (p<0.01). In anterior/posterior direction the humeral head was more centered at 60 and 90 degrees of abduction during muscle activity. The data demonstrate the importance of neuromuscular control in providing joint stability. The technique developed can also be used for investigating the effect of muscle dysfunction and their relevance on the mechanics of the shoulder joint.

Biomechanical Phenomena↗
PubMed2000

Validation of high-resolution water-excitation magnetic resonance imaging for quantitative assessment of thin cartilage layers.

OBJECTIVE: To employ a magnetic resonance (MR) imaging technique for quantitative assessment of thin cartilage layers, and to validate the cartilage volume and thickness measurements. METHODS: We investigated 10 normal elbow joints (age 20 to 69 years) with a 3D gradient echo sequence with selective water excitation (TR 18 ms; TE 9 ms; FA 25 degrees, resolution 1x0.25x0.25 mm2, imaging time 19 min). After interpolating the image data to a 0.125x0.125 mm2 in-plane resolution, the cartilage plates were segmented, reconstructed in 3D, and the cartilage volume and thickness determined with a 3D Euclidean distance transformation algorithm, independent of the original section plane. The cartilage volume and thickness values were compared with CT arthrography and A-mode ultrasound. RESULTS: The mean systematic difference between the elbow cartilage volume obtained from MR imaging and CT arthrography was -0.11% (-6.0 mm3) and the mean random difference 5.7% (314 mm3). Except for the fovea capitis radii, the deviations were not statistically significant (range -7.6 to +11.7%). In the humerus, the mean cartilage thickness (average = 1.35 mm) was overestimated relative to CT arthrography (+20.7%/+0.23 mm), and slightly underestimated relative to A-mode ultrasound (-6.0%/-0.05 mm). With few exceptions, there were no significant differences between MRI, CT arthrography and ultrasound in the other joint surfaces of the elbow (random deviations between 0.08 and 0.39 mm). CONCLUSIONS: The technique presented can be applied for determining the cartilage volume and 3D thickness in joints with thin cartilage layers with a reasonable degree of accuracy.

Adult↗
PubMed2000

A technique for 3D in vivo quantification of proton density and magnetization transfer coefficients of knee joint cartilage.

OBJECTIVE: To develop an MR-based method for the in vivo evaluation of the structural composition of articular cartilage. DESIGN: Five sagittal magnetic resonance imaging (MRI) protocols were acquired throughout the knee joint of 15 healthy volunteers and the boundaries of the cartilage segmented from a previously validated sequence with high contrast between cartilage and surrounding tissue. The other sequences were matched to these data, using a 3D least-squares fit algorithm to exclude motion artefacts. In this way secondary images were computed that included information about the proton density (interstitial water content) and the magnetization transfer coefficient (macromolecules, collagen). The average signal intensities of the 3D cartilage plates were extracted from these data sets and related to a phantom. RESULTS: The signal intensity data showed a high interindividual variability for the proton density (patella 31%, lateral tibia 36%, medial tibia 29%); the patella displaying higher values than the tibia (P< 0.001). There were high correlations between the three plates. The magnetization transfer coefficient also showed high variability (patella 25%, lateral tibia 32%, medial tibia 30%) with the lowest values in the medial tibia (P< 0.01) and lower correlations between the plates. The slice-to-slice variation (medial to lateral) ranged from 9% to 24%. CONCLUSION: An MR-based method has been developed for evaluating the proton density and magnetization transfer of articular cartilage in vivo and observing systematic differences between knee joint cartilage plates. The technique has the potential to supply information about the water content and collagen of articular cartilage, in particular at the early state of osteoarthritic degeneration.

Adult↗
PubMed2000

Magnetic resonance-based motion analysis of the shoulder during elevation.

Changes in shoulder motion patterns are relevant in various shoulder diseases, but no in vivo information exists about the relative positions in vivo of the shoulder girdle bones and the supraspinatus muscle in three-dimensional space. Thus, the objective of this study was to perform a motion analysis of these structures during passive arm elevation using open magnetic resonance imaging and three-dimensional image processing. Fourteen volunteers were examined in five positions of abduction (30 degrees-150 degrees) with an open magnetic resonance system. After segmentation and three-dimensional reconstruction, the axis of the supraspinatus, humerus, clavicle, and the plane of the glenoid were determined, and the relative movements were calculated. The ratio for glenohumeral to scapulothoracic motion was 1.5:1 at 60 degrees and 2.4:1 at 120 degrees abduction. At 30 degrees, the axis of the supraspinatus was nearly horizontal, and during abduction a continuous elevation (+123 degrees at 150 degrees abduction) was measured. In the transverse plane, the angle between the supraspinatus and the clavicle axes became larger during abduction because of an increasing retroversion of the clavicle. The study shows specific three-dimensional motion patterns for each bone of the shoulder girdle and the supraspinatus muscle during passive elevation. The technique and results can be used for future studies in patients with pathologic changes of shoulder girdle motion.

Adult↗
PubMed1999

Determination of 3D cartilage thickness data from MR imaging: computational method and reproducibility in the living.

The objective of this work was to develop a computational approach for quantifying the three-dimensional (3D) thickness distribution of articular cartilage with magnetic resonance (MR) imaging, independent of the imaging plane, and to test the reproducibility of the method in the living. An algorithm was implemented, based on a 3D Euclidean distance transformation, and its accuracy was assessed in geometric test objects, for which an analytic solution was available. The precision of the method was evaluated in six replicated MR data sets of the knee joint cartilage of eight volunteers. The algorithm produced 3D thickness values identical to those of the analytic solutions in the test objects. The reproducibility of the mean cartilage thickness in the patellar and tibial cartilages was 1.5-3.4% (root-mean-square average of the individual coefficient of variation percent), that of the maximal thickness 2.1-7.9%, and that of the thickness distribution 2.3-6.1%. The method presented allows for noninvasive analysis of 3D cartilage thickness from MR images in biomechanical and clinical investigations.

Algorithms↗
PubMed1999

Subacromial space width changes during abduction and rotation--a 3-D MR imaging study.

The objectives of this study were to determine systematic changes of the normal subacromial space width during abduction and rotation, and to analyze the spatial relationship of the supraspinatus muscle with the acromion and clavicle. 12 healthy volunteers were imaged by an open MR scanner in 5 different positions of abduction and in 3 positions of rotation. After three dimensional (3D) reconstruction and 3D Euclidian distance transformation, the minimal spatial distances between the humerus and the acromion and the humerus and clavicle were computed. The minimal acromio-humeral distance decreased significantly from 30 degrees of abduction (mean 7.0 mm +/- 1.6 mm) to 120 degrees (mean 3.9 mm; +/- 1.8 mm; p < 0.0001). At 30 degrees, the minimal distance penetrated the supraspinatus, whereas at 120 degrees it was always located lateral to the supraspinatus tendon. At 90 degrees with internal rotation (7.6 mm, +/- 2.3 mm) the minimal acromio-humeral distance was larger than in neutral rotation (5.4 mm, +/- 2.3 mm) or external rotation (4.4 mm, +/- 2.2 mm; p < 0.05), but it penetrated the supraspinatus tendon at its most vulnerable part, reaching the acromion at its anterior inferior border. We conclude that the subacromial space width changes during abduction and rotation and that the supraspinatus is in closest contact to the anterior inferior border of the acromion in 90 degrees of abduction with 45 degrees internal rotation. These values obtained in volunteers can be used as a basis for further investigations in patients with the impingement syndrome.

Acromion↗
PubMed1999

A non-destructive technique for 3-D microstructural phenotypic characterisation of bones in genetically altered mice: preliminary data in growth hormone transgenic animals and normal controls.

A non-destructive, three-dimensional technique for microstructural phenotypic characterisation of skeletal elements in genetically altered mice is presented. Preliminary data in bovine growth-hormone transgenic animals and control littermates are shown. The technique is based on microcomputed tomography (microCT) and digital postprocessing and allows for a differential quantitative analysis of the cortical and trabecular bone compartments in the axial and peripheral skeleton. The distal femora and the first lumbar vertebral bodies of six animals were CT scanned in the axial plane with an isotropic resolution of 20 microm. The periostal surface and the marrow spaces were segmented fully automatically, and the trabecular and cortical compartments were separated interactively. After 3-D reconstruction, various regions of interest (diaphyseal, metaphyseal and epiphyseal) were selected for the analysis. The femora and vertebrae of the transgenic animals showed obvious differences in size, shape, and trabecular arrangement compared with the control animals. The total bone mass was increased by a factor of two to three, but the trabecular bone was increased much more (up to 12 times) than the cortical bone. The transgenic animals showed an increased ratio of trabecular vs cortical bone (0.90 to 1.27 vs 0.14 to 0.36 in the femoral diaphysis) and an elevated trabecular bone volume fraction (49% to 73% vs 18% to 43% in the femoral metaphysis). The mean 3-D cortical thickness was similar in the normal and transgenic animals (values between 93 microm and 232 microm in the dia- and metaphyses), but the minimal cortical thickness was lower in the transgenic animals (22 to 31 microm vs 54 microm to 110 microm in the diaphysis). The technique presented is suitable for phenotypic characterisation of bone structure in genetically altered mice.

Animals↗
PubMed1999

In situ measurement of articular cartilage deformation in intact femoropatellar joints under static loading.

The deformational behavior of articular cartilage has been investigated in confined and unconfined compression experiments and indentation tests, but to date there exist no reliable data on the in situ deformation of the cartilage during static loading. The objective of the current study was to perform a systematic study into cartilage compression of intact human femoro-patellar joints under short- and long-term static loading with MR imaging. A non-metallic pneumatic pressure device was used to apply loads of 150% body weight to six joints within the extremity coil of an MRI scanner. The cartilage was delineated during the compression experiment with previously validated 2D and 3D fat-suppressed gradient echo sequences. We observed a mean (maximal) in situ deformation of 44% (57%) in patellar cartilage after 32 h of loading (mean contact pressure 3.6 MPa), the femoral cartilage showing a smaller amount of deformation than the patella. However, only around 7% of the final deformation (3% absolute deformation) occurred during the first minute of loading. A 43% fluid loss from the interstitial patellar matrix was recorded, the initial fluid flux being 0.217 +/- 0.083 microm/s, and a high inter-individual variability of the deformational behavior (coefficients of variation 11-38%). In conjunction with finite-element analyses, these data may be used to compute the load partitioning between the solid matrix and fluid phase, and to elucidate the etiologic factors relevant in mechanically induced osteoarthritis. They can also provide direct estimates of the mechanical strain to be encountered by cartilage transplants.

Adolescent↗
PubMed1999

Interobserver reproducibility of quantitative cartilage measurements: comparison of B-spline snakes and manual segmentation.

The objective of this work was to develop a segmentation technique for thickness measurements of the articular cartilage in MR images and to assess the interobserver reproducibility of the method in comparison with manual segmentation. The algorithm is based on a B-spline snakes approach and is able to delineate the cartilage boundaries in real time and with minimal user interaction. The interobserver reproducibility of the method, ranging from 3.3 to 13.6% for various section orientations and joint surfaces, proved to be significantly superior to manual segmentation.

Cartilage, Articular↗