SEARCH · Search PubMed

Results for “Elasticity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,045 records · Page 58Linked to original sources

PubMed2003

Relationship between aortic-to-radial arterial pressure gradient after cardiopulmonary bypass and changes in arterial elasticity.

BACKGROUND: An aortic-to-radial arterial pressure gradient may develop during and after cardiopulmonary bypass (CPB). The mechanisms of this pressure gradient remain controversial. To clarify the cause of the pressure gradient after CPB, the authors investigated the relationship between the pressure gradient and changes in the pulse wave velocity (PWV) before and after CPB. METHODS: The pressure gradient from the aorta to the radial artery and a change in PWV were measured with a wire (0.37 mm in diameter) tipped with a miniature pressure transducer in 12 patients undergoing cardiac surgery. The pressure distributions and waveforms were measured and recorded with electrocardiograph. The PWV was calculated by measuring the propagation time between the R wave of the electrocardiograph and the rising point of the arterial pressure waveform at 10-cm intervals. RESULTS: After CPB, 7 of 12 patients demonstrated a marked pressure gradient. In these patients, the pressure distribution showed a gradual decrease toward the periphery without a precipitous step-down in pressure at any one specific anatomic location. The PWV decreased as the intraarterial pressure decreased from the aorta to the radial artery, and the relative arterial elasticity decreased linearly toward the periphery. CONCLUSIONS: The results showed that the decrease in PWV implies a decrease in arterial elasticity, and the decrease in the arterial elasticity correlated with the decrease in intraarterial pressure. These findings demonstrated that a radial artery pressure lower than the aortic pressure after CPB may be due to the decrease in arterial elasticity.

Adult↗

PubMed1977

Elastic tissue dysplasia of the internal carotid artery.

Elongation with kinking of the internal carotid artery is not an uncommon finding. Cerebral vascular insufficiency has been reported secondary to this abnormality. Although arteriosclerosis is a frequent cause in adults, the etiology in children has never been explained. Three children with significant kinking of the internal carotid artery are reported here. Each underwent surgical correction by excision and reconstruction. Histological review showed the elastic tissue to be disrupted, diminished in amount, and unevenly distributed. Retrospective examination of this elastic tissue dysplasia showed it to be localized, there being normal morphology both proximally and distal to the involved area. There was recurrence of elongation and kinking in one patient due to incomplete excision. Correction was accomplished after re-excision of the involved tissue with a vein graft interposition. From this study, it can be concluded that elongation and kinking of the internal carotid artery in children is secondary to elastic tissue dysplasia. It is imperative that the entire involved area be removed in order to prevent recurrence. The excised specimen should be studied histologically with elastic tissue stains. Such stains cannot be performed as frozen section. Should permanent studies show the margins of resection not to be beyond the dysplastic tissue, careful followup of these children is essential to recognize recurrence.

Carotid Artery Diseases↗

PubMed1995

Fibrin structure and concentration alter clot elastic modulus but do not alter platelet mediated force development.

During clot retraction, platelets interact with fibrin resulting in marked reduction of clot volume. Altered fibrin structure has been reported to affect clot retraction as measured by serum expression. This study was performed to test whether such altered retraction was the result of increased resistance to network collapse or due to decreased force development by platelets. Altered fibrin structure was documented as variation of fibre mass/length ratios (mu) and shifts in clot elastic modulus. The force developed by platelets during clotting was measured directly. Increasing the fibrinogen concentration led to thinner fibre formation (decreased mu), and a linear increase in gel elastic modulus. Over a fibrinogen concentration range of 100 to 400 mg/dl, force development was minimally affected. Force development and clot elastic modulus increased in a linear fashion with increasing platelet concentration. Increasing the calcium concentration from 5 to 20 mM caused a 160% increase in fibrin fibre size (mu), and a 52% decline in clot modulus. Force developed at 1200 s declined by 17%. At 15 mg/ml, dextran and hydroxyethyl starch (HES) also increased mu, and decreased clot modulus; however, both agents markedly reduced force development. Increasing ionic strength or the addition of IgG decreased mu and increased gel elastic modulus. Force development increased modestly with increased ionic strength, did not change with addition of IgG in saline and declined with addition of IgG in maltose. This study indicates that force development is primarily dependent on platelet function while clot modulus depends on both fibrin structure and platelet function.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Coagulation↗

PubMed1983

Elastic properties of the human chest during cardiopulmonary resuscitation.

Sternal displacement during CPR was measured in 11 adults and 2 manikins (Recording Resusci Anne) while the chest was compressed with variable maximum pulse compression force at a rate of 60/min with compression duration of 0.5-0.6 sec. In 10 patients, the pulsatile sternal elastic characteristic can be satisfactorily described with a 2nd degree polynomial F = beta Ds + gamma D2s, where beta = 54.9 +/- 29.4 (mean +/- SD) N/cm is the pulsatile initial elasticity and gamma = 10.8 +/- 4.1 N/cm2 is the posterior resiliency. The sternal characteristics of manikins were linear F = kDs with high elasticity constants, k = 131 and 142 N/cm. Therefore, the manikins tested differ significantly in elasticity characteristics from the human chest during resuscitation. In general, the manikin: (1) has markedly greater stiffness at the onset of compression, and (2) maintains a linear stiffness throughout the usual range of displacement, rather than becoming stiffer with greater chest displacement.

Adolescent↗

PubMed1994

Effects of two low-osmolar contrast media, ioxaglate and iopamidol, on erythrocyte membrane elasticity.

RATIONALE AND OBJECTIVES: The effect of ioxaglate and iopamidol, two recently developed low-osmolality contrast media, on the shear elasticity of erythrocyte membranes was studied at an iodine concentration of 300 mg/mL and at a 20% volume concentration and compared with that obtained for control solutions matched in osmolality. METHODS: The authors used a micromanipulation technique, which consists of visualizing deformations of individual erythrocytes when gently aspirated into the tip of a glass micropipette by an accurately controlled pressure. An erythrocyte membrane shear elasticity modulus mu was then deduced. An increase in mu corresponded to an increase in erythrocyte membrane rigidity. RESULTS: In all cases, the erythrocytes remained discocytic. The shear elasticity modulus of the erythrocyte membrane is found to be (1) in the presence of ioxaglate (4.3 +/- 0.9 microN/m) lower (P < .001) than in the presence of hyperosmolar saline (6.2 +/- 1.3 microN/m) and lower (P < .02) than in the presence of iso-osmolar control (4.7 +/- 0.7 microN/m); (2) in the presence of iopamidol (5.4 +/- 0.7 microN/m) lower (P < .001) than in the presence of hyperosmolar sucrose (6.4 +/- 1.2 microN/m) and higher (P < .001) than in the presence of iso-osmolar control (4.7 +/- 0.7 microN/m); and (3) lower (P < .001) in the presence of ioxaglate (4.3 +/- 0.9 microN/m) than in the presence of iopamidol (5.4 +/- 0.7 microN/m). CONCLUSIONS: Under the experimental conditions used, both contrast media (ioxaglate and iopamidol) modify the erythrocyte membrane shear elasticity modulus less than do the matched hyperosmolar controls. Moreover, ioxaglate makes the erythrocyte membrane less rigid, and iopamidol makes the erythrocyte membrane more rigid than does the iso-osmolar control.

Elasticity↗

PubMedDate not supplied

Relationships between young modulus of elasticity, ash density, and MRI derived effective transverse relaxation T2* in tibial specimens.

OBJECTIVE: It has been hypothesized that the MR relaxation time T2* of bone marrow present in the intertrabecular spaces may be related to the density of the trabecular network and may be a predictor of trabecular bone properties. MATERIALS AND METHODS: To derive a relationship between the marrow relaxation time T2* and biomechanical properties of trabecular bone, we studied two sets of trabecular bone specimens from human tibiae. The first set consisted of 12 specimens that were defatted and immersed in saline; the second set consisted of 18 specimens with marrow in the trabecular spaces. The MR studies were conducted on a 1.5 T imaging system. In the first set of specimens, a GE sequence (TR = 70 ms; TE = 5, 10, 15, 20, 25 ms) was used to obtain images in the axial plane. In the second set, a water suppression pulse was used prior to an asymmetric SE sequence (TR = 300 ms; TE = 4, 8, 12, 16, 20, 24 ms) to obtain images in the axial, coronal, and sagittal planes. The T2* of the intertrabecular saline of the marrow fat was calculated assuming a monoexponential decay. In both sets, the elastic moduli were measured in three orthogonal directions (superoinferior, anteroposterior, and mediolateral). The ash density was determined after the completion of the experiments. RESULTS: Our results indicate a moderate significant negative correlation between T2* and ash density or elastic modulus (E) in both sets of specimens. The correlation coefficients were slightly improved between the transverse relaxation rate 1/T2* and bone density or E. We found a good correlation between T2* and the reciprocal ash density (r = 0.88) and between T2* and the reciprocal elastic modulus 1/E (r = 0.87 to r = 0.95) in the first set, while in the second set the correlation remained moderate. With use of a multiple linear regression model (1/E = a x T2* + b x 1/T2* + n), the reciprocal elastic moduli 1/E were predicted to > 90% by T2* and 1/T2* in the first set of specimens. This finding was not replicated with the second set of specimens. In the second set of specimens, we found poor to moderate correlation coefficients between the T2* times in the three orthogonal planes (r = 0.45 to r = 0.71). CONCLUSION: Trabecular bone properties such as density and strength may potentially be assessed with quantitative MR techniques. However, especially for in vitro studies, specimen preparation, acquisition parameters, and specimen geometry may have a significant impact on the obtained results.

Bone Density↗

PubMed2003

Effect of MTAD on flexural strength and modulus of elasticity of dentin.

The purpose of this study was to evaluate the effect of MTAD on the flexural strength and modulus of elasticity of dentin. Dentin bars were randomly assigned to eight groups treated with various concentrations of NaOCl (5.25%, 2.65%, 1.31%, 0.66%), 17% EDTA, MTAD, saline, or according to a clinical protocol with 1.3% NaOCl and then 5 min of MTAD. Specimens were subjected to flexural strength and modulus of elasticity tests. Two-sample t test (alpha = 0.05) showed no statistically significant differences between various groups except for a reduction in flexural strength for the 2-h MTAD group (p = 0.002) and the EDTA group (p = 0.002). A significant reduction of modulus of elasticity for the 2-h MTAD group (p < 0.001), EDTA group (p < 0.001), and 0.6% NaOCl (p < 0.002) also was noted. There was no significant difference in flexural strength and modulus of elasticity between the dentin bars exposed to saline or MTAD when applied according to the clinical protocol (p > 0.05). These results indicate that MTAD can be used as prescribed for clinical use without affecting the physical properties of the dentin.

Analysis of Variance↗

PubMed1997

The elastic modulus of conductance coronary arteries from spontaneously hypertensive rats is increased.

OBJECTIVE: To assess the alterations of morphological and functional properties of conductance coronary and mesenteric resistance arteries in spontaneously hypertensive rats (SHR). DESIGN: The in-vitro intrinsic elastic properties of the wall material in SHR coronary arteries were determined in comparison with those of Wistar-Kyoto (WKY) rats. Mesenteric resistance arteries from rats of both strains were also studied. METHODS: Arterial segments were cannulated at both ends using an arteriograph system and subjected to pressure increments with simultaneous measurements of the wall thickness and internal diameter. The strain, stress and incremental elastic modulus (Einc) were calculated from diameter-pressure curves. RESULTS: Over the full range of pressures tested (10-160 mmHg), the internal diameters of SHR coronary arteries were not significantly different from those of WKY rat arteries, whereas we observed that SHR mesenteric resistance arteries had a significantly smaller diameter. The stress-strain curve for coronary arteries was shifted significantly to the left-hand side for the SHR group indicating more stress per unit strain, whereas the opposite was found for mesenteric resistance arteries. When Einc was determined under isobaric conditions, we found no difference between SHR and WKY rat coronary arteries, whereas this parameter was decreased significantly for SHR mesenteric resistance arteries. When Einc was estimated at the respective operating pressures, it was 1.7- to 2.8-fold greater for SHR than it was for WKY rat mesenteric resistance and coronary arteries. Moreover, the total collagen area: lumen area ratio was significantly greater for the SHR than it was for the WKY rat coronary artery wall, but this ratio was similar for mesenteric preparations from the two strains. CONCLUSION: These results show that, at a given stress or operating pressure level, the material of SHR coronary artery wall is characterized by an increase in Einc, whereas there is no increase in Einc for in mesenteric resistance arteries. This functional alteration is accompanied by an increase in the relative proportion of collagen, a component with a high elastic modulus, in the wall. In contrast, we found no change in elastic modulus and in the relative proportion of collagen for the SHR mesenteric resistance arteries. Furthermore, the present results support the hypothesis that alterations in distensibility differ among the components of the SHR vasculature.

Animals↗

PubMed2001

A morphological study of age changes in adult human auricular cartilage with special emphasis on elastic fibers.

OBJECTIVE: It is well known that the size of the human auricle increases after it has finished development. The reason why the size of the human auricle continues to enlarge until advanced age after reaching adulthood was investigated by observation of the ultrastructure of elastic fibers in human auricular cartilage. METHODS: A total of 1958 subjects (966 males and 992 females) were classified into 18 age groups from 0 to 5 years up to 85 years and above by 5-year intervals. Ear length, ear width, and length of ear attachment were measured with calipers. Human auricular cartilage was obtained from 26 subjects (16 males and 10 females) aged 14 to 79 years, stained by orcein, and examined by light and electron microscopy. RESULTS: Each item of measurement of human auricular size increased significantly with age in both males and females. On morphological examination by light and electron microscopy after orcein staining, elastic fibers in the cartilage were almost homogeneous in diameter and surrounded the cartilage lacuna in bundle-like fashion in young persons, whereas those in elderly persons were heterogeneous in thickness and had many fragments surrounding the territorial matrix. In elderly persons, collagen-like fibers and small vesicles with heterogeneous electron density were frequently observed near elastic bundles around the territorial matrix. CONCLUSION: Structural changes of auricular cartilage associated with morphological age changes of elastic fibers may be one of the causes of expansion of the auricle after reaching adulthood.

Adolescent↗

PubMed1988

Elasticity of the bovine sclera measured with real-time holographic interferometry.

Real-time holographic interferometry was used to evaluate the elasticity of the posterior scleral hemisphere of fresh and preserved enucleated bovine eyes. Absolute amplitude values of radial distension were determined for specific locations across the sclera as the tissue was subjected to minute increases in intraocular pressure (IOP). Results indicate that different locations on the globe possess different coefficients of elasticity. Specifically, the supralateral aspect of the posterior globe distended relatively more than the inframedial and medial portions of the globe. Elastic moduli were derived by an areal method in which strain was measured as a change in surface area of the globe, and stress was measured as a change in IOP. Coefficients of elasticity in the range of 3.9 to 9.0 megapascals (MPa) were determined for locations across the posterior scleral hemisphere of the fresh eye used in this study.

Animals↗

PubMed1997

The effect of chemosurgical peels and dermabrasion on dermal elastic tissue.

Chemosurgical peel is a technique that has been used widely by plastic surgeons and dermatologists to remove fine and deep wrinkles of the skin. However, the reaction of elastic tissue to the cutaneous application of commonly used chemical peeling agents has not been defined. This study comparatively assessed the alteration in dermal histology and mechanical properties of skin following treatment with 25% and 50% trichloroacetic acid, Baker's phenol solution, and dermabrasion. Yucatan minipigs served as the animal model. The skin was analyzed at five intervals over 6 months after treatment using histologic, quantitative, and mechanical analysis (hematoxylin and eosin, elastic tissue, and Sirius red stains, computerized digital morphometry, and a tensiometer). At 6 months we found no change in the quality, structure, or arrangement of elastic fibers in skin treated with a single application of 25% and 50% trichloroacetic acid or dermabrasion when compared with untreated skin. Skin treated with Baker's phenol solution showed a marked morphologic change in the elastic fibers. The fibers within the regenerated zone of dermis were sparse, wispy, and immature at 6 months after treatment. Preliminary tensiometric analysis of phenol-treated skin at 6 months indicated that the skin was stiffer and weaker. This study questions the possibility of long-term change to the skin by the deep penetration of caustic chemicals to remove wrinkles and rejuvenate the skin.

Animals↗

PubMed2002

Comparison of arterial elasticity measured in left and right arms using the HDI/Pulsewave CR-2000 Research System.

BACKGROUND: Arterial elasticity is implicated as a risk factor for or a marker of cardiovascular disease. Current advances in non-invasive devices have now made it possible to measure arterial elasticity in an ambulatory setting. OBJECTIVE: The aim of this study was to determine whether there is a difference in blood pressure and arterial elasticity measured in the right and the left arms. METHODS: Simultaneous measurements were performed with two HDI/Pulsewave CR-2000 Research CardioVascular Profiling Systems. The manufacturer recommends placing the blood pressure cuff on the left upper arm and the sensor on the skin overlying the right radial artery. We followed the manufacturer's recommendations and also placed both the cuff and the sensor on the same arm. Simultaneous measurements were made on both arms with both machines. The average of three measurements was used for each combination. Systolic and diastolic blood pressure, and large-artery and small-artery elasticity indices, were determined for each subject and used in the analysis. RESULTS: The subjects were 11 males and 9 females between 22 and 46 (33.5 +/- 7.4 years) years of age. There was no significant difference in the average difference for each test combination. CONCLUSION: Thus, when using the HDI/Pulsewave CR-2000 Research CardioVascular Profiling System, the blood pressure cuff and the sensor can be placed on either the same arm or opposite arms.

Adult↗

PubMed2006

Aortic elastic properties and left ventricular diastolic function in white-coat hypertensive individuals.

OBJECTIVES: Although white-coat hypertension may be present in 25% or more of hypertensive individuals, its prognostic significance and predisposition to end organ damage is unknown. To evaluate whether white-coat hypertension is associated with end organ damage, we compared prognostically relevant measures of target-organ damage among 35 individuals with white-coat hypertension and age and sex-matched groups of sustained hypertension and normotensive individuals classified by clinical and 24-h ambulatory blood pressures. METHODS: We evaluated left ventricular diastolic function and aortic elastic properties of 35 individuals with white-coat hypertension, 50 patients with sustained hypertension, and 35 normotensive healthy volunteers using transthoracic Doppler echocardiography. None of the study participants with sustained hypertension and white-coat hypertension, who were newly diagnosed and never treated, had any systemic disease or coronary risk factor except hypertension. RESULTS: Age, sex, and body mass indexes were similar among the three groups. Left ventricular diastolic function was more significantly impaired in the sustained hypertension and white-coat hypertension groups than in the control group, but it was not significantly different between the white-coat hypertension and sustained hypertension groups. Aortic distensibility was significantly lower, and aortic stiffness index was significantly higher in the sustained hypertension group than in the white-coat hypertension and control groups. Furthermore, aortic elastic properties were slightly impaired in the white-coat hypertension group compared with those in the control group. We also found a significant correlation between aortic elastic properties and left ventricular diastolic function. CONCLUSIONS: White-coat hypertension may alter left ventricular diastolic function and aortic elastic properties. These alterations, however, might not be as remarkable as those caused by sustained hypertension. In this respect, individuals with white-coat hypertension are not at such a risk for end organ damage as patients with sustained hypertension.

Adolescent↗

PubMed2006

Impaired aortic elastic properties in young patients with prehypertension.

OBJECTIVES: Although hypertension has been shown to be one of the most important predictors of reduced arterial elasticity, there is not enough data about aortic elastic properties in patients with prehypertension. Accordingly, the current study was designated to evaluate aortic elastic features in young patients with prehypertension. MATERIAL AND METHODS: The study population consisted of 25 newly diagnosed prehypertensive individuals (18 men, mean age=34+/-6 years) and 25 healthy controls (16 men, mean age=33+/-6 years) eligible for the current study. Aortic strain, distensibility index and stiffness index beta were calculated from aortic diameters measured by echocardiography and blood pressures simultaneously measured by sphygmomanometry. RESULTS: Prehypertensive patients were detected to have significantly lower aortic distensibility and strain indexes than the controls: (5.77+/-1.91 vs. 8.63+/-2.67 cm dynx10, respectively, P<0.001; strain index: 13.81+/-4.50 vs. 17.47+/-4.25%, respectively, P=0.005). Aortic stiffness index beta of the prehypertensive group, however, was significantly higher than that of the control group (3.73+/-1.41 vs. 2.97+/-0.82, P=0.02). CONCLUSION: Whatever the mechanism, young patients with prehypertension have impaired aortic elasticity compared with healthy controls. This finding has suggested that the development of overt hypertension may be prevented or delayed by using the agents that have the ability to reduce arterial stiffness by regressing and/or preventing functional and structural changes on the arterial wall.

Adult↗

PubMed2004

Thermal fluctuations of small rings of intrinsically helical DNA treated like an elastic rod.

It is shown that the writhe distribution in a collection of thermally fluctuating rings formed from intrinsically helical DNA treated like an elastic rod can be determined completely from a knowledge of the dependence of the configuration integral on the intrinsic geometric torsion of the rods. When the length of the rods is of the order of the persistence length or less, the configuration integral can be expressed in terms of the frequencies of the normal modes of the rings, and so these torsion-dependent frequencies then become the quantities of interest. The nature of the normal modes of rings formed from intrinsically helical elastic rods, as deduced from the equations of motion in the Kirchhoff-Clebsch theory of the dynamics of elastic rods, is described. Examples of computed writhe distributions are given. The observed broadening of the writhe distribution as the intrinsic curvature of the rods is increased is shown to be related to the stability properties of the circular equilibrium configuration of the elastic rods. These results thus imply that thermal fluctuations in small rings of intrinsically curved DNA will be more pronounced than in rings of the same size formed from intrinsically straight DNA.

Base Sequence↗

PubMed2000

Elastic stability of DNA configurations. I. General theory.

Results are presented in the theory of the elastic rod model for DNA, among which are criteria enabling one to determine whether a calculated equilibrium configuration of a DNA segment is stable in the sense that it gives a local minimum to the sum of the segment's elastic energy and the potential of forces acting on it. The derived stability criteria are applicable to plasmids and to linear segments subject to strong anchoring end conditions. Their utility is illustrated with an example from the theory of configurations of the extranucleosomal loop of a DNA miniplasmid in a mononucleosome, with emphasis placed on the influence that nicking and ligation on one hand, and changes in the ratio of elastic coefficients on the other, have on the stability of equilibrium configurations. In that example, the configurations studied are calculated using an extension of the method of explicit solutions to cases in which the elastic rod modeling a DNA segment is considered impenetrable, and hence excluded volume effects and forces arising from self-contact are taken into account.

Biophysical Phenomena↗

PubMed2005

Elasticity of polymer vesicles by osmotic pressure: an intermediate theory between fluid membranes and solid shells.

The entropy of a polymer confined in a curved surface and the elastic free energy of a membrane consisting of polymers are obtained by scaling analysis. It is found that the elastic free energy of the membrane has the form of the in-plane strain energy plus Helfrich's curvature energy [Z. Naturforsch. C 28, 693 (1973)]. The elastic constants in the free energy are obtained by discussing two simplified models: one is the polymer membrane without in-plane strains and asymmetry between its two sides, which is the counterpart of quantum mechanics in a curved surface [H. Jensen and H. Koppe, Ann. Phys. (N.Y) 63, 586 (1971)]; the other is the planar rubber membrane with homogeneous in-plane strains. The equations to describe equilibrium shape and in-plane strains of the polymer vesicles by osmotic pressure are derived by taking the first-order variation of the total free energy containing the elastic free energy, the surface tension energy, and the term induced by osmotic pressure. The critical pressure above which a spherical polymer vesicle will lose its stability is obtained by taking the second-order variation of the total free energy. It is found that the in-plane mode also plays an important role in the critical pressure because it couples with the out-of-plane mode. Theoretical results reveal that polymer vesicles possess mechanical properties intermediate between those of fluid membranes and solid shells.

Computer Simulation↗

PubMed1999

Elastic model-based segmentation of 3-D neuroradiological data sets.

This paper presents a new technique for the automatic model-based segmentation of three-dimensional (3-D) objects from volumetric image data. The development closely follows the seminal work of Taylor and Cootes on active shape models, but is based on a hierarchical parametric object description rather than a point distribution model. The segmentation system includes both the building of statistical models and the automatic segmentation of new image data sets via a restricted elastic deformation of shape models. Geometric models are derived from a sample set of image data which have been segmented by experts. The surfaces of these binary objects are converted into parametric surface representations, which are normalized to get an invariant object-centered coordinate system. Surface representations are expanded into series of spherical harmonics which provide parametric descriptions of object shapes. It is shown that invariant object surface parametrization provides a good approximation to automatically determine object homology in terms of sets of corresponding sets of surface points. Gray-level information near object boundaries is represented by 1-D intensity profiles normal to the surface. Considering automatic segmentation of brain structures as our driving application, our choice of coordinates for object alignment was the well-accepted stereotactic coordinate system. Major variation of object shapes around the mean shape, also referred to as shape eigenmodes, are calculated in shape parameter space rather than the feature space of point coordinates. Segmentation makes use of the object shape statistics by restricting possible elastic deformations into the range of the training shapes. The mean shapes are initialized in a new data set by specifying the landmarks of the stereotactic coordinate system. The model elastically deforms, driven by the displacement forces across the object's surface, which are generated by matching local intensity profiles. Elastic deformations are limited by setting bounds for the maximum variations in eigenmode space. The technique has been applied to automatically segment left and right hippocampus, thalamus, putamen, and globus pallidus from volumetric magnetic resonance scans taken from schizophrenia studies. The results have been validated by comparison of automatic segmentation with the results obtained by interactive expert segmentation.

Algorithms↗