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At least 883 records · Page 49Linked to original sources
PubMed2006

Accurate calibration of a stereo-vision system in image-guided radiotherapy.

Image-guided radiotherapy using a three-dimensional (3D) camera as the on-board surface imaging system requires precise and accurate registration of the 3D surface images in the treatment machine coordinate system. Two simple calibration methods, an analytical solution as three-point matching and a least-squares estimation method as multipoint registration, were introduced to correlate the stereo-vision surface imaging frame with the machine coordinate system. Both types of calibrations utilized 3D surface images of a calibration template placed on the top of the treatment couch. Image transformational parameters were derived from corresponding 3D marked points on the surface images to their given coordinates in the treatment room coordinate system. Our experimental results demonstrated that both methods had provided the desired calibration accuracy of 0.5 mm. The multipoint registration method is more robust particularly for noisy 3D surface images. Both calibration methods have been used as our weekly QA tools for a 3D image-guided radiotherapy system.

Calibration↗
PubMedDate not supplied

Simulator mounted Moiré topography camera for constructing compensating filters.

A technique has been developed and implemented by which individualized Ellis compensating filters can be rapidly and accurately produced from Moiré topographic photographs. A novel Moiré camera has been designed such that it has been possible to mount it on a radiotherapy simulator. The camera does not interfere with normal use of the simulator but can be deployed as needed. Depth of missing tissue contours are produced by the camera over the treatment field, accurately registered to the patient's simulated treatment position. An optical enlargement technique is used to transfer the depth of missing tissue contours in the photograph to a lead sheet compensating filter.

Humans↗
PubMed1981

Stereological analysis of plasmolysis in logarithmic-phase Bacillus licheniformis.

The plasmolytic response of Bacillus licheniformis 749/C cells to the increasing osmolarity of the surrounding medium was quantitated with stereological techniques. Plasmolysis was defined as the area (in square micrometers) of the inside surface of the bacterial wall not in association with bacterial membrane per unit volume (in cubic micrometers) of bacteria. This plasmolyzed surface area was zero when the cells were suspended in a concentration of sucrose solution lower than 0.5 M, but increased linearly when the sucrose molarity rose above 0.5 M, reaching a plateau value of 3.61 micrometers2/micrometers3 in 2 M sucrose. In contrast, when the bacterial cells were treated with lysozyme plasmolysis increased abruptly from 0.06 micrometers2/micrometers3 in 0.75 M sucrose to 4.09 micrometers2/micrometers3 in 1 M sucrose. When the time of exposure was prolonged, the degree of plasmolysis increased gradually for the duration of the experiment (30 min) after exposure to 1 M sucrose without lysozyme, whereas with lysozyme plasmolysis reached a maximum (4.09 micrograms2/micrometers3) in 2 to 5 min. The examination of ultrastructure showed that the protoplast bodies of lysozyme-treated cells in 1 M sucrose and untreated cells in 2 M sucrose are maximally retracted from the intact wall of the bacteria; hardly any retraction of protoplasts could be seen for untreated cells in 1 M sucrose. The data suggest that the B. licheniformis cells are isoosmotic to 800 to 1,100 mosM solutions, but are able to withstand much greater osmotic pressure with no signs of plasmolysis because the cell wall and the plasma membrane are held in close association, perhaps by a covalent bond. It is likely that lysozyme weakens this bond by degradation of the peptidoglycan layer. Cellular autolysis also weakens this wall-membrane association.

Bacillus↗
PubMed1982

Structure of the regular surface layer of Aquaspirillum serpens MW5.

The structure of the regular surface layer of Aquaspirillum serpens MW5 has been investigated by electon microscopy supplemented by computer image processing and least-squares analysis. The layer has a ribbed appearance, both on the bacterium and in isolated, negatively stained fragments. However, detailed analysis indicated that the layer was composed of two hexagonal sheets having p6mm symmetry and a = 16 nm. One sheet was staggered by one half repeat along a (1,0) line of the p6nm lattice relative to the second so that, in projection, the pattern of the composite layer was a translational moiré, characterized by a series of ribs spaced 16 nm apart. The ribbed layer had cmm symmetry with a = 32 nm and b = 18.5 nm. Analysis of this pattern indicated that the two p6nm hexagonal sheets were unevenly stained, and this was confirmed by using least-squares methods to simulate the observed pattern by combining two hexagonal patterns. The general structure of the layer was consistent with a role as a selective and protective barrier on the cell surface.

Cell Membrane↗
PubMed1981

Stereophotogrammetry and relief photography in the assessment of foot disorders.

Expanded polyethylene foam (Plastazote) is used in the treatment of rheumatoid, diabetic, and leprotic foot disorders. This paper describes a diagnostic use for this material. Two photographic techniques combine to give vivid and quantitative representations of foot deformities which are easily applicable to clinical use. Relief photography uses illumination to create an illusion of solidity in a 2-dimensional photography. Stereophotogrammetry produces contour plots from stereopairs of photographs of the Plastazote footprint. After use the impressions are trimmed and slipped into the patient's shoes in the same way as any other foam insole.

Dermatoglyphics↗
PubMed2006

Comparison of disc damage likelihood scale, cup to disc ratio, and Heidelberg retina tomograph in the diagnosis of glaucoma.

AIM: To evaluate the relative diagnostic strength of cup to disc (C/D) ratio, clinical disc damage likelihood scale (DDLS), a new clinical method of documenting glaucomatous optic disc changes, and Heidelberg retina tomograph (HRT-II) in patients with glaucoma, glaucoma suspects, and normal controls. METHOD: Consecutive observational case series. 110 eyes from 110 patients categorised as glaucoma, glaucoma suspect, or normal were examined clinically to grade the DDLS score. HRT-II examination was performed by an examiner masked to the clinical examination findings. Optic disc parameters and Moorfields regression analysis findings were recorded. Stereophotographs of the optic disc were examined independently by two glaucoma specialists in masked fashion to determine the C/D ratio. Zeiss SITA Standard 24-2 visual fields were obtained within 3 months of HRT-II and clinical examination. For each patient, the eye with the worse mean deviation of the visual field test was enrolled in the study, and each field was additionally graded by the four level Hodapp-Parrish-II-Anderson staging. Specificity and sensitivity were calculated by receiver operating characteristic (ROC) curves. RESULTS: Mean patient age was 58 years (SD 13.3) with 45 glaucoma patients, 23 glaucoma suspects, and 42 normals. The mean deviation on Humphrey visual field assessment using SITA-Standard was -4.95 D (SD 5 D) Clinical examination using DDLS had the best predictive power with an area under the ROC curve value of 0.95 when glaucoma patients and suspects were separated from borderline or normals. This was followed by clinical examination of C/D ratio (0.84), and HRT-II Moorfields analysis (0.68). The order of diagnostic strength did not change when definite glaucoma was compared to borderline and normals. CONCLUSIONS: The DDLS grading performs well compared to C/D ratio and HRT-II evaluation. Attention to disc diameter and to rim width may increase the value of clinical optic disc examination.

Adolescent↗
PubMed2006

Three dimensional optic disc visualisation from stereo images via dual registration and ocular media optical correction.

BACKGROUND/AIMS: The three dimensional (3-D) visualisation of the optic disc in true colour will give essential meaning in clinical application. It is not only useful for clinicians in the evaluation of the condition of the optic disc, but it also simplifies the pathological diagnosis and disease progression monitoring. This paper describes a complete 3-D optic disc reconstruction method from a pair of stereo images by a series of robust procedures including camera calibration, image registration, depth recovery, and ocular media optical inclusion. METHODS: Two registration techniques (correlation and feature based methods) are combined together to prune the uncertain matching points in order to improve the overall accuracy of registration. The ocular media within the eyeball are lump modelled as a single lens and integrated into the reconstruction process to obtain an accurate 3-D optic disc image. CONCLUSION: The recovered 3-D optic disc images show good consistency and compatibility when compared with the results from Heidelberg retina tomography (HRT) under clinical validation, with an additional advantage of implementing a more economical and conventional mode of retinal image acquisition.

Algorithms↗
PubMed2003

Comparison of two reference standards in validating two field mydriatic digital photography as a method of screening for diabetic retinopathy.

AIM: To compare two reference standards when evaluating a method of screening for referable diabetic retinopathy. METHOD: Clinics at Oxford and Norwich Hospitals were used in a two centre prospective study of 239 people with diabetes receiving an ophthalmologist's examination using slit lamp biomicroscopy, seven field 35 mm stereophotography and two field mydriatic digital photography. Patients were selected from those attending clinics when the ophthalmologist and ophthalmic photographer were able to attend. The main outcome measures were the detection of referable diabetic retinopathy as defined by the Gloucestershire adaptation of the European Working Party guidelines. RESULTS: In comparison with seven field stereophotography, the ophthalmologist's examination gave a sensitivity of 87.4% (confidence interval 83.5 to 91.5), a specificity of 94.9% (91.5 to 98.3), and a kappa statistic of 0.80. Two field mydriatic digital photography gave a sensitivity of 80.2% (75.2 to 85.2), specificity of 96.2% (93.2 to 99.2), and a kappa statistic of 0.73. In comparison with the ophthalmologist's examination, two field mydriatic digital photography gave a sensitivity of 82.8% (78.0 to 87.6), specificity of 92.9% (89.6 to 96.2), and a kappa statistic of 0.76. Seven field stereo gave a sensitivity of 96.4% (94.0 to 98.8), a specificity of 82.9% (77.4 to 88.4), and a kappa statistic of 0.80. 15.3% of seven field sets, 1.5% of the two field digital photographs, and none of the ophthalmologist's examinations were ungradeable. CONCLUSION: An ophthalmologist's examination compares favourably with seven field stereophotography, and two field digital photography performs well against both reference standards.

Adult↗
PubMed1988

Retrospective geometric correlation of MR, CT, and PET images.

Magnetic resonance imaging, computed tomographic, and positron emission tomographic studies of the brain provide complementary information, and many patients undergo more than one of these studies during the course of their diagnostic workup and treatment. A new technique for quantitative geometric correlation of such studies makes it possible to create integrated multimodality images by mapping features from one image onto an image obtained with another modality. The coordinate transformation between any pair of images is found by a semiautomatic algorithm for matching models of the patient's external surface as depicted in the two data sets. The resultant hybrid images, which combine complementary features of different studies, are often more useful for diagnosis and treatment planning than are the original single-modality images. The algorithm can also be used for spatial registration of baseline studies with follow-up images created with the same modality, which allows tracking of a lesion to detect subtle interval changes in size and shape. This technique can be applied to images acquired in routine clinical practice, since it is completely retrospective and does not necessitate special positioning or landmarking of the patient.

Adolescent↗
PubMedDate not supplied

Stereoscopic display of a three-dimensional image of the larynx using high-speed helical scanning.

To evaluate the usefulness of stereoscopic images of larynges using helical CT in stereo mode, a retrospective review of the characteristics of stereoscopic viewing of larynges was made. The subjects were 3 patients with laryngeal cancer, 1 patient with laryngeal leiomyosarcoma and 1 patient with an advanced tongue carcinoma whose formalin-fixed larynx was extirpated. The larynges were scanned by high-speed helical CT using 1- to 2-mm slices. The reproduction of stereographic images was performed by the manipulation and rotation of three-dimensional structures around the y-axis on the computer display. The three-dimensional images of the complex structures, such as the arytenoid cartilage, aryepiglottic fold and pyriform sinus, were better observed by binocular images (stereograms) than by monocular images. Stereoscopic views of the larynx are useful in producing three-dimensional images of the unseen inner surface of the human body.

Adult↗
PubMed2002

Collagenase-induced changes in articular cartilage as detected by electron-microscopic stereology, quantitative polarized light microscopy and biochemical assays.

The purpose of this study was to compare the ability of electron-microscopic (EM) stereology with quantitative polarized light microscopy (PLM) and biochemical collagen (hydroxyproline) and crosslink (pyridinoline) analyses to detect changes in the superficial collagen network of bovine articular cartilage after digestion in vitro with purified bacterial (Clostridium histolyticum) collagenase (30 U/ml) for 24 and 48 h. Collagen volume (V(V)) and surface (S(V)) densities of the uppermost third of the superficial zone were estimated indirectly from zonal isotropic uniform random sections using collagen length density (L(V)) and average collagen fibril diameter, or its average second power. Collagenase digestion caused a significant decrease in fibril diameter (64 to 62%), V(V) (89 to 95%) and S(V) (64 to 86%) after incubation for 24 and 48 h. Collagen L(V) remained unchanged after 24 h incubation but decreased 63% after 48 h. Collagen concentration per dry weight, assayed biochemically from the whole superficial zone, decreased also significantly (29 to 60%) after 24 and 48 h digestions, respectively. The pyridinoline concentration per dry weight of the superficial zone decreased (31 to 57%) whereas the pyridinoline concentration per collagen remained unchanged. PLM revealed that the birefringence of the uppermost third of the superficial zone was decreased by 36% after digestion for 24 h though the total birefringence of the whole zone was not reduced. However, after 48 h, the birefringence of the whole superficial zone was significantly reduced (76%). All of the techniques compared in this study could detect collagen network degradation in bovine articular cartilage but the EM stereological technique was more sensitive at detecting the changes than PLM or biochemical assays.

Animals↗
PubMed1983

Pattern of membranous and chondral bone growth. A roentgen stereophotogrammetric analysis in the rabbit.

To elucidate longitudinal tubular bone growth patterns in relation to craniofacial development, nine 4-week-old male New Zealand white rabbits received tantalum implants in the calvarial bones and in the proximal and distal tibial epiphyses. The animals were examined by roentgen stereophotogrammetry. The rapid growth rate deceleration pertained to all growth regions studied, except the sagittal suture. A brief period of under-nutrition highlighted the parallel in growth rates between the frontonasal suture (associated to the facial skeleton) and the tibia. The neurocranial coronal suture exhibited a different growth pattern, presumably related to neural tissue expansion, which was also observed to rapidly react to nutritional deficiency. Tibial growth was found to sensitively reveal influences of somatic development. Hence, it might be used to optimize growth evaluations.

Animals↗
PubMed1987

Study of the cuspal ridges of the upper first molars in a modern Japanese population.

Materials used were dental casts of the upper first molars of modern Japanese subjects, comprising 29 males and 25 females. Their molar occlusal surfaces were photographed by moiré contourography using the standard trigonal plane. The ridges of a cusp, comprising a central ridge and mesial and distal accessory ridges, were identified from the patterns of the moiré fringes. The central ridge was observed in all cusps except for the hypocone in both sexes. Frequencies of the mesial and distal accessory ridges of trigonal cusps were over 90% except for the distal accessory ridge of the metacone, and those of the hypocone were under 25% in both sexes. These values were generally higher in males than in females, especially for the distal accessory ridge of the metacone. The running pattern of the cuspal ridges showed little difference between sexes. The oblique ridge which was higher than the central groove formed a saddle-like structure. This ridge was observed in all materials, but its heights and structural components varied remarkably. In this study, the distal accessory ridge of the metacone was found to be incorporated into the oblique ridge in about 13% of cases. Variability in the running pattern of the ridges within a single cusp was highest in the hypocone and lowest in both the paracone and protocone. The results obtained are considered to represent the stability or reductive tendency of cusps in the upper first molars.

Child↗