Biological response modifiers in rheumatoid arthritis.
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Antibodies, Monoclonal↗
Biomedical subjects
D Mitton
Publications and source records attributed to D Mitton.
Simplified calibration system for stereoradiography in scoliosis.
Stereoradiography is a well known method to obtain 3D images of the spine and the thorax. The main algorithm used is the DLT, which is a very general one yielding to 11 implicit parameters per view. In order to calibrate the geometrical configuration of the stereoradiographic setup with this algorithm, there is a need of a wide calibrating object, leading to systems hard to use in clinical practice. The aim of this work was to modify the algorithm in order to simplify the calibration object. We used assumptions related to the specific case of stereoradiography, which reduced the problem of calibration to only 6 independent explicit parameters. A geometrical calibration performed plane by plane enabled to design a singular calibration object composed of steel balls along two vertical lines and three horizontal ones. A simulation of real configuration both for the previous method and the current algorithm associated to the singular calibrating object give for thirty 3D points a 2 RMS (95% confidence interval) error of reconstruction of respectively 0.6 and 0.3 mm. This study yielded to the transfer in clinics of two simplified systems of calibration which will be easier to use in clinical practice.
Calibration↗
3D detailed reconstruction of vertebrae with low dose digital stereoradiography.
As scoliosis requires a global and local 3D examination of the spine in standing position, stereoradiography appears as one of the most adequate 3D imaging tool for it diagnosis. Our purpose was to increase the geometry definition of the stereoradiographic reconstruction to obtain morpho-realistic models and to validate them using 41 dry vertebrae. Our results propose 2000 points 3D personalised models without any loss of accuracy in comparison to previous studies.
Algorithms↗
Pre and post 3D modeling of scoliotic patients operated with in situ contouring technique.
A three-dimensional segmental analysis was performed on the stereoradiographic reconstructions of ten right thoracic scoliotic patients. From the quantitative model of the spine and pelvis, the vertebral and intervertebral orientations were computed pre and post operatively. These orientations allow to determine the apical and junctional zones of the high thoracic, thoracic and lumbar curves. The apical zone corresponds to the maximum of vertebral axial rotation. Pre operatively, the tendency was T7 for the thoracic transverse apex with 20 AE of axial rotation. The junctional zone corresponds to the maximum of vertebral lateral rotation and the maximum of intervertebral axial rotation. The tendency was T5 and T12 for the junctional vertebrae of the thoracic curve with, at both levels, 30 AE of vertebral lateral rotation and 10 AE of intervertebral axial rotation. The surgical correction obtained by in situ contouring technique was evaluated through these 3D orientations. The vertebral axial rotation at the high thoracic, thoracic and lumbar apex was corrected with respectively 52%, 60% and 60%.
Adolescent↗
Prevention of postoperative wound haematomas and hyperperfusion following carotid endarterectomy.
OBJECTIVE: To study the incidence of wound haematomas and hyperperfusion following carotid endarterectomy and the effect of changes in perioperative management. METHODS: We undertook a prospective audit of the postoperative outcome of 300 consecutive carotid endarterectomies performed for a symptomatic stenosis of the internal carotid artery, under the care of a single consultant. RESULTS: audit of the first 100 operations between 1990-93 resulted in 4 changes to clinical practice. These included the use of Dacron instead of vein because of 3 vein patch blowouts, invasive postoperative monitoring of blood pressure, and the use of intravenous beta-blockers to control hypertension, because of 4 hyperperfusion injuries. The use of 10F suction drains was discontinued, because they did not prevent 8 wound haematomas. The results of the second 100 cases between 1994-97 and the third 100 cases between 1998-2000 confirmed no further hyperperfusion injuries or patch blowouts (p =0.01 and 0.04 respectively). Larger 14F suction drains were reintroduced for the third series because of thirteen haematomas in the second series (p =0.09). Only 4 haematomas occurred in the third series ( p =0.05). The need for beta-blockers fell in the third series due to the introduction of local anaesthesia (p =0.0001). CONCLUSION: The use of Dacron patches and postoperative control of hypertension has reduced the incidence of haemorrhage and hyperperfusion after carotid endarterectomy. Larger suction drains may also help.
Adrenergic beta-Antagonists↗
Retrograde stripping of recurrent varicose veins.
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Humans↗
3D reconstruction method from biplanar radiography using non-stereocorresponding points and elastic deformable meshes.
Standard 3D reconstruction of bones using stereoradiography is limited by the number of anatomical landmarks visible in more than one projection. The proposed technique enables the 3D reconstruction of additional landmarks that can be identified in only one of the radiographs. The principle of this method is the deformation of an elastic object that respects stereocorresponding and non-stereocorresponding observations available in different projections. This technique is based on the principle that any non-stereocorresponding point belongs to a line joining the X-ray source and the projection of the point in one view. The aim is to determine the 3D position of these points on their line of projection when submitted to geometrical and topological constraints. This technique is used to obtain the 3D geometry of 18 cadaveric upper cervical vertebrae. The reconstructed geometry obtained is compared with direct measurements using a magnetic digitiser. The order of precision determined with the point-to-surface distance between the reconstruction obtained with that technique and reference measurements is about 1 mm, depending on the vertebrae studied. Comparison results indicate that the obtained reconstruction is close to the actual vertebral geometry. This method can therefore be proposed to obtain the 3D geometry of vertebrae.
Cervical Vertebrae↗
An investigation of segmentation methods and texture analysis applied to tomographic images of human vertebral cancellous bone.
The goal of this study is to determine architectural and textural parameters on computed tomographic (CT) images, allowing us to explain the mechanical compressive properties of bone. Although the resolution (150 microm) is of the same order of magnitude as the trabecular thickness, this method enables the possibility of perfecting an in vivo peripheral CT system with an acceptable radiation dose for the patient. This study was performed on L2 vertebrae cancellous bone specimens taken after necropsy in 22 subjects aged 47-95 years (mean: 79 years). The segmentation process is a crucial point in the determination of accurate architectural parameters. In this paper the use of two different segmentation methods is investigated, based on an edge enhancement and a region growing approach. The images are compared and the architectural parameters extracted from the images segmented by both methods lead to a quantitative evaluation. The parameters are found to be globally robust towards the segmentation process, although some of them are much more sensitive to the approach used. Highly significant correlations (P < 0.0005) have been obtained between the two segmentation methods for all the parameters, with rho ranging from 0.70 to 0.93. In order to improve the assessment of bone architecture, texture analysis (run length method) was investigated. New features are obtained from an image reduced to 16 grey-levels. Textural parameters in addition to architectural parameters in a multivariate regression model increase significantly (P = 0.01) the prediction of the maximum compressive strength (variation of r2 from 0.75 up to 0.89).
Aged↗
High-resolution computed tomography for architectural characterization of human lumbar cancellous bone: relationships with histomorphometry and biomechanics.
The aim of the present study on human vertebral cancellous bone was to validate structural parameters measured with high-resolution (150 microm) computed tomography (HRCT) by referring to histomorphometry and to try to predict mechanical properties of bone using HRCT. Two adjacent vertical cores were removed from the central part of human L2 vertebral body taken after necropsy in 22 subjects aged 47-95 years (10 women, 12 men; mean age 79 +/- 14 years). The right core was used for structural analysis performed by both HRCT and histomorphometry. Two cancellous bone specimens were extracted from the left core: a cube for HRCT and a compression test, and a cylinder for a shear test. Significant correlations were found between HRCT and histomorphometric measurements (BV/TV, trabecular thickness, separation and number, and node-strut analysis), but with higher values for most of the tomographic parameters (BV/TV and trabecular thickness determined by HRCT were overestimated by a factor 3.5 and 2.5 respectively, as compared with histomorphometry). The maximum compressive strength and Young's modulus were highly correlated (rho = 0.99, p<0.0005). Significant correlation was obtained between bone mineral density (determined using dual-energy X-ray absorptiometry) and the maximum compressive strength (rho = 0. 64, p = 0.002). In addition the maximum compressive strength and architectural parameters determined by HRCT or histomorphometry showed significant correlations (e.g., for HRCT, BV/TV: rho = 0.88, p<0.0005, N.Nd/TV: rho = 0.73, p<0.001). The shear strength was significantly correlated with BV/TV (rho = 0.62, p = 0.002), Tb.Sp (rho = -0.58, p = 0.004) and TSL (rho = 0.55, p = 0.006) measured by HRCT. In conclusion, an HRCT system with 150 microm resolution is not sufficient to predict the true values of the structural parameters measured by histomorphometry, although high correlations were found between the two methods. However, we showed that a resolution of 150 microm allowed us to predict the mechanical properties of human cancellous bone. In vivo peripheral systems with such a resolution should be of interest and would deliver an acceptable radiation dose to the patient.
Aged↗
Mechanical properties of ewe vertebral cancellous bone compared with histomorphometry and high-resolution computed tomography parameters.
The goal of the present study was to determine if a high-resolution computed tomography (HRCT) system with 150 microns resolution was sufficient to predict mechanical properties in ewe lumbar vertebrae. To answer this question, we used a triangular comparison between: HRCT; biomechanics (compression and shear tests); and histomorphometry, which was the reference method for the measurements of morphometric parameters. Two dissected lumbar vertebrae (L-4 and L-5) from 32 ewes were used. Both compressive and shear properties correlated significantly with amount of bone and structural parameters evaluated by histomorphometry (bone volume/tissue volume, trabecular thickness, trabecular separation), but no significant correlation was found with the trabecular number. With our shear test involving the trabecular architecture itself more significant correlations were found with the node-strut analysis parameters than from the compressive test. Significant correlations were also found between HRCT and histological parameters (bone volume/tissue volume, bone surface/bone volume, trabecular separation, trabecular number, total strut length, number of nodes, and number of termini). Correlations between HRCT structural parameters and mechanical properties on L-4 were of the same magnitude as the correlations between the histomorphometric structural parameters and mechanical results on L-5 but with the remarkable advantage the HRCT is a noninvasive method. In spite of the resolution (150 microns) of our HRCT system, which entailed mainly an enlargement of the thinnest trabeculae or their loss during the segmentation process, we obtained coherent relationships between mechanical and tomographic parameters. The thinnest trabeculae probably had little effect on the mechanical strength. Also, this type of resolution allows us to consider the possibility of perfecting an in vivo HRCT system. However, physical density and bone mineral density correlated much better with strength than either classical histomorphometric or tomographic parameters. The current conclusion is fairly negative with respect to the ability of HRCT to assess mechanical properties nondestructively as compared with dual-energy X-ray absorptiometry. But, the noninvasive nature of the imaging modality and the capacity for three-dimensional imaging at arbitrary orientation make HRCT a promising tool in the quantitative assessment of cancellous architecture.
Animals↗
The effects of density and test conditions on measured compression and shear strength of cancellous bone from the lumbar vertebrae of ewes.
An animal model (the ewe) was used to study mechanical parameters of cancellous bone specimens. Compression and shear tests were conducted on ewe vertebral trabecular bone (L1-L5) from old ewes (mean age: 9 years) under two different conditions: first, at room temperature in air ("standard" test conditions); and secondly, in a physiological saline bath regulated at 37 degrees C. The parameters obtained under "standard" test conditions with a uniaxial compression test were the mean value of the maximum strength (sigma max = 22.3 (7.06) MPa), Young's modulus (E = 1510 (784) MPa), the strain at maximum strength (epsilon sigma max = 3.21 (0.8) percent) and the energy absorbed during the test (W = 0.3 (0.12) MJ.m-3). No significant change was found when the test was carried out in a saline bath at 37 degrees C (p < 0.0005). An original shear test was performed to evaluate the shear strength which was found to vary from 7.5 (4.7) to 14.6 (8.53) MPa under "standard" test conditions depending on the method of calculation. Testing of the specimens in a 37 degrees C physiological saline bath induced a decrease in the shear strength from 32.5 percent (p < 0.0005) to 37.3 percent (p < 0.0001) of those measured under "standard" test conditions. The non-destructive measurement of the Bone Mineral Density (BMD) accounted for up to 73.3 percent of the maximum compressive strength sigma max and 61.5 percent of the maximum shear strength tau max determined in saline solution at 37 degrees C. These results showed that other parameters influencing the mechanical properties of trabecular bone and its structure appeared to be essential.
Absorptiometry, Photon↗
Comparison between bone density and bone strength in glucocorticoid-treated aged ewes.
In order to assess if bone densitometry could be used as an indicator to evaluate bone fragility in short term studies performed on glucocorticoid-treated ewes, correlations between DXA measurements and biomechanical parameters obtained on the same bones were established in 27 aged ewes including sixteen animals treated with methylprednisolone 15 mg/day for 4 months and eleven untreated animals. DXA measurements were performed ex-vivo on HOLOGIC QDR-1000+ device. Biomechanical testings included a three-point bending test on the femur and a compression test on cylinders of cancellous bone excised from two lumbar vertebrae selected between L6 and L4. At the femoral site, bone mineral density was correlated with the bending stiffness (r = 0.65) and the ultimate bending strength (r = 0.64) whereas, at the vertebral site, biomechanical parameters failed to correlate with bone mineral density assessed by DXA. This apparent lack of correlation between vertebral bone mass and trabecular bone strength is mainly linked to anatomical characteristics of the ewe: in this species, the vertebral posterior arches, which consist mainly of cortical bone, are very large compared to the vertebral body and strongly influence the bone mineral density evaluated on the intact vertebra. This is not the case with other large animals, for instance non-human primates. In conclusion, DXA can give a good evaluation of bone strength for ewe femurs, but results must be interpreted carefully at the vertebral site due to the anatomical characteristics of this animal species.
Absorptiometry, Photon↗