SEARCH · PubMed Health

Results for “computational morphology”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 361 records · Page 20Linked to original sources

PubMed2005

Neural correlates of lexicon and grammar: evidence from the production, reading, and judgment of inflection in aphasia.

Are the linguistic forms that are memorized in the mental lexicon and those that are specified by the rules of grammar subserved by distinct neurocognitive systems or by a single computational system with relatively broad anatomic distribution? On a dual-system view, the productive -ed-suffixation of English regular past tense forms (e.g., look-looked) depends upon the mental grammar, whereas irregular forms (e.g., dig-dug) are retrieved from lexical memory. On a single-mechanism view, the computation of both past tense types depends on associative memory. Neurological double dissociations between regulars and irregulars strengthen the dual-system view. The computation of real and novel, regular and irregular past tense forms was investigated in 20 aphasic subjects. Aphasics with non-fluent agrammatic speech and left frontal lesions were consistently more impaired at the production, reading, and judgment of regular than irregular past tenses. Aphasics with fluent speech and word-finding difficulties, and with left temporal/temporo-parietal lesions, showed the opposite pattern. These patterns held even when measures of frequency, phonological complexity, articulatory difficulty, and other factors were held constant. The data support the view that the memorized words of the mental lexicon are subserved by a brain system involving left temporal/temporo-parietal structures, whereas aspects of the mental grammar, in particular the computation of regular morphological forms, are subserved by a distinct system involving left frontal structures.

Adult↗

PubMed2006

Robust rigid registration of retinal angiograms through optimization.

Retinal fundus photographs are employed as standard diagnostic tools in ophthalmology. Serial photographs of the flow of fluorescein and indocyanine green (ICG) dye are used to determine the areas of the retinal lesions. For objective measurements of features, the registration of the images is a necessity. In this paper, we employ optimization techniques for registration with the help of 2-parameter translational motion model of retinal angiograms, based on non-linear pre-processing (Wiener filtering and morphological gradient) and computation of the similarity criteria for the alignment of the two gradient images for any given rigid transformation. The optimization methods are effectively employed to minimize the similarity criterion. The presence of noise, the variations in the background and the temporal variation of the fluorescence level pose serious problems in obtaining a robust registration of the retinal images. Moreover, local search strategies are not robust in the case of ICG angiograms, even if one uses a multiresolution approach. The present work makes a systematic comparison of different optimization techniques, namely the minimization method derived from the optical flow formulation, the Nelder-Mead local search and the HCIAC ant colony metaheuristic, each optimizing a similarity criterion for the gradient images. The impact of the resolution and median filtering of gradient image is studied and the robustness of the approaches is tested through experimental studies, performed on macular fluorescein and ICG angiographies. Our proposed optimization techniques have shown interesting results especially for high resolution difficult registration problems. Moreover, this approach seems promising for affine (6-parameter motion model) or elastical registrations.

Algorithms↗

PubMed1998

Sixty adrenal masses of large dimensions: hormonal and morphologic evaluation.

OBJECTIVES: To evaluate the nature and function of adrenal masses of large dimensions (macrotumors). METHODS: Sixty consecutive patients (31 women, 29 men, age range 15 to 84 years) with adrenal masses 4.0 cm in diameter or larger (range 4.0 to 15.0 cm) underwent morphologic study by computed tomography (CT); the majority also underwent 131-I-6beta-norcholesterol (131I-NC) or 131I-MIBG scintigraphy. Basal evaluation of glucocorticoids, mineralcorticoids, and catecholamines was performed in all patients, and in 38 cases determination of androgens was also made. In addition, on the basis of various clinical suspicions, a dynamic hormonal study was performed. RESULTS: Macrotumors were benign in 78.3% of cases and included pheochromocytomas (n = 17), nonfunctioning cortical adenomas (n = 12), and cortisol-secreting tumors (n = 7, Cushing's syndrome). Malignant forms were 21.7% of the total, including pheochromocytomas (n = 3), cortical carcinomas (n = 6), and metastases (n = 4). On CT, malignant masses were larger (8.4+/-0.9 cm) than benign ones (5.7+/-0.3 cm) (P < 0.0001) and the mass size was strictly related to malignancy (P < 0.03). CT did not offer other diagnostic criteria for malignancy, except irregular margins and regional lymph node enlargement, which were more frequently (P < 0.0001) found in malignant forms. 131I-MIBG scintigraphy showed tracer uptake in all pheochromocytomas, both benign and malignant. By contrast, on 131I-NC scintigraphy, cortical malignancies never accumulated the radiotracer, whereas uptake was observed in all cases of solid cortical benign adenomas. Patients with cortical carcinomas showed plasma sex steroids above the normal range, pheochromocytomas were asymptomatic in 15% of cases, and almost half of the patients with Cushing's syndrome did not show clinical features of the disease (pre-Cushing's syndrome). CONCLUSIONS: Adrenal macrotumors frequently show endocrine activity and the medulla seems to be involved more than the cortex. Pheochromocytomas and cortisol-secreting adenomas are sometimes asymptomatic. Malignancy is often found in macromasses and, at least for the cortical forms, size of the tumor on CT, 131I-NC uptake on scintigraphy, and determination of levels of sex steroids seem to be useful criteria for predicting the nature of the mass.

Adolescent↗

PubMed1997

Imaging and staging of avascular osteonecroses at the wrist and hand.

Avascular ostenecroses (AVN) are unspecific focal sceletal lesions of vascular origin. At the wrist, AVNs are mainly seen in the lunate (Kienbock's disease) and the proximal scaphoid fragment in the presence of a nonunion disease (pseudarthrosis). Other types of osteonecroses are rare. The natural process of devitalization proceeds in steps: initially, there is a bone marrow oedema, followed by trabecula sclerosis, cystic transformation of the spongiosa, and bone fragmentation. End stages include carpal collapse (SLAC wrist) and osteoarthritis. For imaging of the sceletal morphology in AVN computed tomography is most useful, whereas initial stages and perfusion damages are better detected with contrast enhanced magnetic resonance imaging (MRI). In this paper a staging classification for Kienböck's disease and the scaphoid nonunion, considering the diagnostic and therapeutic consequences, is presented.

Diagnosis, Differential↗

PubMed2005

Interactions between polymers and carbon nanotubes: a molecular dynamics study.

We used force-field-based molecular dynamics to study the interaction between polymers and carbon nanotubes (CNTs). The intermolecular interaction energy between single-walled carbon nanotubes and polymers was computed, and the morphology of polymers adsorbed to the surface of nanotubes was investigated. Furthermore, the "wrapping" of nanotubes by polymer chains was examined. It was found that the specific monomer structure plays a very important role in determining the strength of interaction between nanotubes and polymers. The results of our study suggest that polymers with a backbone containing aromatic rings are promising candidates for the noncovalent binding of carbon nanotubes into composite structures. Such polymers can be used as building blocks in amphiphilic copolymers to promote increased interfacial binding between the CNT and a polymeric matrix.

Journal Article↗

PubMed1999

Early prenatal diagnosis of cord entanglement in monoamniotic multiple pregnancies.

OBJECTIVES: Cord entanglement is a severe complication in monoamniotic multiple pregnancies. Three cases were reviewed to determine how early ultrasound diagnosis might improve counselling and management. METHODS: In two monoamniotic twin and one dichorionic diamniotic triplet pregnancies, cord entanglement was detected between 10 and 18 gestational weeks by color Doppler and pulsed Doppler velocimetry. Pregnancies were followed up on a weekly basis with special observation of fetal behavior and use of color Doppler velocimetry. RESULTS: In Case 1, a monoamniotic twin pregnancy with cord entanglement close to the umbilical insertions was diagnosed at 10 weeks. Longitudinal follow-up showed intrauterine death of both twins at 15 weeks. In Case 2, entanglement of the umbilical cords of two monoamniotic triplets within a dichorionic diamniotic triplet pregnancy was diagnosed at 10 weeks. The pregnancy continued uneventfully until 35 weeks when cord entanglement was confirmed at Cesarean section. All triplets have since developed normally. In Case 3, monoamniotic twins were diagnosed at 18 weeks. Color Doppler detected side-by-side insertion of the umbilical cords and Doppler velocimetry suggested an entanglement at the chorionic plate. The pregnancy was complicated by polyhydramnios. Cesarean section at 36 weeks confirmed cord entanglement at the chorionic plate. Postnatal computer angiography and morphological examination of the placenta showed the presence of superficial artery-to-artery and vein-to-vein anastomoses and of deep arteriovenous shunts. The development of the twins was uneventful. CONCLUSIONS: Diagnosis of cord entanglement is feasible early in gestation. Future protocols are proposed to document the gestational age at detection, the location, and the Doppler flow patterns and to facilitate the assessment of short- and long-term development.

Adult↗

PubMed1993

[Review of glaucoma research].

This paper reviews publications in the field of glaucoma research from 1991 and 1992. The role of elevated intraocular pressure (IOP) is redefined. Raised IOP is not the only, but probably the most important risk factor in the development of glaucomatous optic nerve damage. The IOP threshold of 20-22 mm Hg may be too high for many patients to avoid progressive damage. Early surgical treatment is more successful than medical or laser treatment and is gaining importance. New techniques have made trabeculectomy safer. In patients with poor surgical prognosis antimetabolites such as 5-fluorouracil or mitomycin C may improve results considerably. However, these treatments need to be defined in their side effects as far as long-term results are concerned. Lasersclerostomy ab interno and ab externo minimize surgical trauma and promise better results in eyes with previous surgery. Contact-cyclo-photocoagulation renders results comparable to cyclo-cryo-coagulation with less perioperative side-effects. However, long-term results must be obtained before it can replace the older technique. Medical treatment on the step to clinical introduction (in Germany) are apraclonidine with less side effects than clonidin, topical carbonic anhydrase inhibitors (dorzolamide) and possibly prostaglandin F2alpha-ester such as PhXA34. Galenic modifications are gelrite, a heteropolymer and betaxolol suspension. Which patients with ocular hypertension to treat and which not to treat still is a therapeutic dilemma. Methods such as colour contrast, investigation of scotopic low-contrast vision and the pattern-electroretinogram promise earlier detection of glaucomatous damage than conventional computer perimetry or morphological methods.

Adrenergic alpha-Agonists↗

PubMed1998

Cerebral functional-morphological match or mismatch in cerebrovascular disease: a comparison of flow-volume SPET, CT findings and Doppler sonography.

Cerebral ischaemia (thromboembolic, haemodynamic) is usually classified according to morphological criteria, but intracerebral rheological aspects often remain underestimated, even though prognosis may depend on areas of reduced perfusion or perfusion reserve around a morphological defect. The aim of this study was to investigate regional haemodynamics in patients with cerebrovascular ischaemia by comparing the size of morphological defects (MD) and perfusion deficits (PD). Ninety patients with cerebrovascular disease were investigated and the size of morphological defects on computed tomography (CT) was compared to the size of perfusion deficits or the extent of exhausted cerebral perfusion reserve (CPR) on a combined flow-volume single photon emission tomographic (SPET) study. Carotid arteries were examined by Doppler ultrasonography. Defect/deficit size ratios of MD, PD and CPR were classified as: (1) CT/SPET mismatch: A (no MD or PD, reduced CPR), B (PD > MD); or (2) CT/SPET match: C (PD = MD). A CT/SPET mismatch was found in 79% of patients with a haemodynamic pattern and in 67% of transient ischaemic attack/reversible ischaemic neurological deficit patients who showed no MD. A mismatch was also found in 21% of patients with thromboembolic infarction. A match was found in 79% of the thromboembolic and in 16% of the haemodynamic infarctions. High grade (> 80%) stenosis of the internal carotid arteries was found in 81% of the mismatch cases, but in only 57% of the match cases. In conclusion, haemodynamic infarctions show a predominance of functional/morphological mismatch, a match being predominant in thromboembolic infarctions. Doppler failed to indicate disturbed intracerebral perfusion in nearly one-fifth of haemodynamically compromised patients. In addition to CT and Doppler, flow-volume SPET enables an assessment of intracerebral haemodynamics which might be relevant for prognosis and therapy.

Brain↗

PubMed2006

P300 is attenuated during dissociative episodes.

The present study examined the pathophysiology of dissociative phenomena using the P300 component of event-related potentials, quantitative electroencephalography (QEEG), and morphology measures of computed tomography scan. Event-related potentials during an auditory oddball paradigm and QEEG in resting state were recorded. Patients exhibited attenuation of P300 amplitudes compared with controls during dissociative episodes, but exhibited recovery to control levels in remission. Patients had a larger Sylvian fissure-brain ratio than did controls. QEEG findings revealed no significant differences between the patients and controls or between episodes and remission in the patient group. Attenuation of the P300 can be interpreted as the result of a negative feedback loop from the medial temporal lobe to the cortex, which decreases the amount of information flow, allocation of attentional resources, and updating of working memory to avoid both excessive long-term memory system activity in medial temporal lobe and resurgence of affect-laden memories.

Acoustic Stimulation↗

PubMed1980

Roentgen cephalometric analysis of ridge resorption and changes in jaw and occlusal relationships in immediate complete denture wearers.

In eighteen subjects assigned for immediate complete upper and lower dentures, roentgen cephalometric recordings were made before extraction of the residual anterior dentition and 3 weeks, 3 months, 6 months and 1 year after denture insertion. The cephalometric analysis was based on electronic measurements of linear and angular morphological variables and computer head plots generated from 177 reference points (Walker, 1967), derived for each subject for each of the five observation stages. The reduction of the alveolar ridges was most rapid during the first 3 months of denture wear and particularly during the post-extraction period of 3 weeks. The reduction in anterior height of the lower ridge was on average twice as great as that of the upper ridge. The ridge resorption and the accompanying settling of the dentures on the basal seats, measured from lead shots inserted in the dentures, brought about an upward rotation of the mandible with a resulting decrease in occlusal vertical dimension and reduction in overjet of the dentures. In accordance with the amount of ridge reduction, these changes showed great individual variation.

Adult↗

PubMed1990

Pancerebellar syndrome in hyperpyrexia.

Two cases of pancerebellar syndrome following hyperpyrexia are described and the relevant literature reviewed. Cranial computed tomography demonstrated morphologic evidence of cerebellar degeneration while the patients were showing satisfactory clinical progress.

Adult↗

PubMed1989

Aging of the diaphragm: a CT study.

To determine the normal morphologic evolution of the diaphragm with aging and to correlate age-related changes with other indicators of physical condition--such as skeletal muscle status, obesity, presence of pulmonary emphysema, and presence of esophageal hiatus hernia--a systematic morphometric and morphologic evaluation of computed tomographic studies of 120 patients from the 3d to 8th decades of life was undertaken. Diaphragm muscle thickness did not change significantly with increasing age. Diaphragmatic defects and pseudotumors, nonexistent in the 3d and 4th decades, increased in number and severity to affect 56% of the patients in the 7th and 8th decades. Neither the status of the skeletal muscle nor the presence of obesity correlated with age or with the presence of diaphragmatic defects. Eighty-four percent of the patients with emphysematous changes demonstrated diaphragmatic defects; thus, a strong association with emphysema was observed. If emphysematous patients are excluded, defects were more common in women. The esophageal hiatus width was found to increase with age.

Adult↗

PubMedDate not supplied

Spectrum of thymic uptake at 18F-FDG PET.

Fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) has emerged as a strong diagnostic tool for the diagnosis and staging of neoplasms. Uptake in the thymus at (18)F-FDG PET complicates the assessment of mediastinal involvement by tumor in children and young adults. Increased thymic (18)F-FDG uptake may represent normal physiologic uptake but may also indicate the presence of thymic hyperplasia, lymphomatous infiltration, primary thymic neoplasm, or metastatic disease. Familiarity with the patterns of (18)F-FDG uptake that characterize these pathologic conditions is crucial to the interpretation of PET findings in the thymus. In addition, awareness of the subsets of patients in whom physiologic uptake may be seen and of the normal morphologic features and (18)F-FDG PET appearance of the thymus, along with a general sense of the upper limits of metabolic activity for physiologic thymic uptake, will aid in differentiating between physiologic thymic uptake and mediastinal disease. In equivocal cases, correlation with morphologic data from computed tomography or magnetic resonance imaging will likely continue to play a key role in diagnosis and will aid in differentiating benign thymic uptake from malignancy.

Fluorodeoxyglucose F18↗

PubMed1991

Why don't all heavy snorers have obstructive sleep apnea?

Patients with obstructive sleep apnea (OSA) and heavy snorers without apnea both show intrathoracic suction pressures during sleep that exceed their static upper airway closing pressures. Complete airway occlusion, however, occurs only in the former patient group. We hypothesized that the kinetic properties of the airflow would be different in these two types of patients because of differences in upper airway morphology. The pharyngeal computed tomography (CT) was used to measure the cross-sectional areas of the upper airways in 15 patients with OSA, 25 nonapneic heavy snorers, and 14 control subjects while they were awake. Nocturnal breathing was monitored with the static charge-sensitive bed (SCSB). The patients with OSA had a narrower airspace at the velopharyngeal (VP) level than the controls (p less than 0.01); the nonapneic snorers did not differ from the other groups. At the tongue base (TB) and the hyoid bone (HB) levels there was no difference between the OSA and the control groups, but the nonapneic snorers had narrower airways at both of these levels compared with control subjects (p less than 0.01) and at the hyoid bone level compared with the OSA group (p less than 0.05). The VP/HB ratio was the parameter that best distinguished the patients with OSA from the nonapneic snorers (lower in the OSA group, p less than 0.001). We suggest that airway collapse during sleep is favored by a narrow velopharynx associated with large hypopharynx. Some heavy snorers may not have an oropharyngeal collapse because the peak inspiratory suction pressure could already be damped down at the level of the relatively narrow hypopharyngeal airways.

Airway Resistance↗

PubMed2007

Time for evidence-based cytology.

Evidence-based medicine (EBM) is a fashionable and an extremely hot topic for clinicians, patients and the health service planners. Evidence-based cytology (EBC) is an offshoot of EBM. The EBC is concerned with generating a reproducible, high quality and clinically relevant test result in the field of cytology. This is a rapidly evolving area with high practical importance. EBC is based entirely on research data. The various professional bodies on cytology design and recommend guidelines on the basis of evidences. Once the guideline is implemented and practiced then the experiences of the practicing cytopathologists may be used as a feed back to alter the existing guideline. The various facets of EBC are sampling and specimen adequacy, morphological identification and computer based expert system, integrated reporting, identification of the controversial areas and high quality researches for evidences. It is the duty of the individuals and institutions to practice EBC for better diagnosis and management of the patients. In this present paper, the various aspects of EBC have been discussed.

Journal Article↗

PubMed2005

99mTc-Annexin A5 uptake and imaging to monitor chemosensitivity.

Most anticancer agents act by inducing apoptosis in sensitive tumor cells. Hence, in many types of cancers, significant increase of tumor apoptosis after chemotherapy correlates with tumor chemosensitivity. Theoretically, a reliable evaluation of apoptotic changes, postchemotherapy to baseline, may provide valuable insights into the apoptotic competence of cancers. Until now, assessment of chemosensitivity has usually relied upon histological evidence of tumor response (i.e., partial or complete disappearance of tumor cells) or demonstration of tumor shrinkage by means of morphological imaging (i.e., computed tomography or magnetic resonance imaging). In clinical practice, however, these conventional methods are proving ineffective for monitoring tumor chemosensitivity on a daily basis. Recent developments in molecular imaging have allowed the synthesis of a new radiolabeled agent, 99mTc-recombinant human Annexin A5, designed to the assessment of apoptotic response of cancers after a single course of chemotherapy. Such in vivo technique opens promising perspectives for evaluating, noninvasively and early, tumor response to anticancer therapies. Alternative methods for Annexin A5 labeling and imaging may improve the detection of drug-induced apoptosis to monitor chemosensitivity.

Animals↗

PubMedDate not supplied

[Qualitative and quantitative evaluation of gastric emptying using a videofluoroscopic method].

We studied the gastric emptying of 21 healthy volunteers using a standard contrasted diet composed of a lipid, carbohydrate, protein and barium sulfate solution homogenate. We did six one-minute videofluoroscopic recordings in a 12-minute interval for the first hour, and in a 30 minute interval until the complete emptying. We selected eight exams for the emptying quantification. We could observe and estimate subjectively the functional behavior and the gastric emptying. Digital representative images of each emptying time point we were able to quantify those observations and describe them as a mathematical function. We developed a macro procedure using the Media Cybernetics ImagePro-Plus software for this quantification. We conclude that: 1--The videofluoroscopic method provides better resolution than the other methods in the analysis of the gastric motility and emptying. 2--It is possible to computationally quantify the morphological differences observed with the sequential registration radiological methods, specially the videofluoroscopic method that generates 30 frames per second. 3--Our results generate a gastric emptying index, based on the area of a gastric projection in radiological images obtained in a standing position over a one-hour period (T1/2). 4--The quantitative analysis should not exclude the qualitative analysis.

Adult↗

PubMed1999

Brain morphology and response to nortriptyline in geriatric depression.

In geriatric patients with major depression (N=15), the authors compared response to treatment with nortriptyline as it relates to brain morphology assessed by computed tomography. There was a significant negative association between ventricle-brain ratio and response to nortriptyline (rs=-0.63; P=0.015).

Aged↗