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Biomedical subjects

C Gyldensted

Publications and source records attributed to C Gyldensted.

At least 37 records · Page 2Linked to original sources
PubMed1997

Comparison of the reliability of craniofacial anatomic landmarks based on cephalometric radiographs and three-dimensional CT scans.

OBJECTIVE: Conventional cephalometry is an inexpensive and well-established method for evaluating patients with dentofacial deformities. However, patients with major deformities, and in particular asymmetric cases are difficult to evaluate by conventional cephalometry. Both two- and three-dimensional computed tomography (CT) have been proposed to alleviate some of these difficulties. Only a few studies using metallic markers have indicated 3-D CT to be a useful diagnostic method, whereas no studies have evaluated the reliability of the anatomic cephalometric points used in 3-D CT. The aim of our study therefore was to compare the reliability of anatomic cephalometric points from conventional cephalograms and 3-D CT. METHODS: Nine human dry skulls were CT scanned. In addition standard lateral and frontal cephalograms were obtained. The CT scans were 3-D image reconstructed, and the cephalometric points were recorded as x, y, and z co-ordinates by two investigators. Computerized cephalometrics were performed-on the lateral and frontal cephalograms. Intra- and interindividual variations were calculated for each method and tested for statistical significance. RESULTS: Lateral cephalogram measures were more reliable than 3-D CT, with interobserver variations less than 1 mm for most points compared to about 2 mm for 3-D CT. Lateral cephalometrics also showed significantly less interobserver variation for six variables. This was, however, less obvious when 3-D CT was compared to frontal cephalograms. Frontal cephalometrics showed significantly less interobserver variation for three of the investigated variables. CONCLUSIONS: For standard lateral and frontal cephalometric points, there is no evidence that 3-D CT is more reliable than the conventional cephalometric methods in normal skull, and the benefit of 3-D CT cephalometric is indicated to be in the severe asymmetric craniofacial syndrome patients, as conventional cephalometrics is known to be inferior in these cases.

Adult↗
PubMed1996

High resolution measurement of cerebral blood flow using intravascular tracer bolus passages. Part I: Mathematical approach and statistical analysis.

The authors review the theoretical basis of determination of cerebral blood flow (CBF) using dynamic measurements of nondiffusible contrast agents, and demonstrate how parametric and nonparametric deconvolution techniques can be modified for the special requirements of CBF determination using dynamic MRI. Using Monte Carlo modeling, the use of simple, analytical residue models is shown to introduce large errors in flow estimates when actual, underlying vascular characteristics are not sufficiently described by the chosen function. The determination of the shape of the residue function on a regional basis is shown to be possible only at high signal-to-noise ratio. Comparison of several nonparametric deconvolution techniques showed that a nonparametric deconvolution technique (singular value decomposition) allows estimation of flow relatively independent of underlying vascular structure and volume even at low signal-to-noise ratio associated with pixel-by-pixel deconvolution.

Cerebrovascular Circulation↗
PubMed1996

High resolution measurement of cerebral blood flow using intravascular tracer bolus passages. Part II: Experimental comparison and preliminary results.

This report evaluates several methods to map relative cerebral blood flow (rCBF) by applying both parametric and nonparametric techniques to deconvolve high resolution dynamic MRI measurements of paramagnetic bolus passages with noninvasively determined arterial inputs. We found a nonparametric (singular value decomposition (SVD)) deconvolution technique produced the most robust results, giving mean gray:white flow ratio of 2.7 +/- 0.5 (SEM) in six normal volunteers, in excellent agreement with recent PET literature values for age-matched subjects. Similar results were obtained by using a model-dependent approach that assumes an exponential residue function, but not for a Gaussian-shaped residue function or for either Fourier or regularization-based model-independent approaches. Pilot studies of our CBF mapping techniques in patients with tumor, stroke, and migraine aura demonstrated that these techniques can be readily used on data routinely acquired by using current echo planar imaging technology. By using these techniques, the authors visualized important regional hemodynamic changes not detectable with rCBV mapping algorithms.

Adult↗
PubMed1996

A comparison of three-dimensional computed tomography scans and stereolithographic models for evaluation of craniofacial anomalies.

PURPOSE: This article describes the use of stereolithographic (SL) models as an adjunct to treatment planning in patients with Apert's syndrome, scaphocephaly, brachycephaly, and turricephaly. PATIENTS AND METHODS: Four syndrome patients had computed tomography (CT) scans done presurgically, and one of these patients was additionally scanned postoperatively. SL models and three-dimensional (3D) CT image reconstructions were produced from the CT data, and linear measurements were compared between the two modalities. RESULTS: All cases showed mean differences between measurements with 3D-CT and SL models of -0.3 to 0.8 mm, except on the CT scans with a gantry tilt (-1.7 mm) and the brachycephalic patient in whom larger deviations were demonstrated (-9.5 mm). CONCLUSION: The results of the study indicate that the accuracy of the SL technique is not always sufficient, necessitating additional validation studies before it can be recommended for routine clinical use.

Acrocephalosyndactylia↗
PubMed1995

[Acoustic neurinomas/vestibular schwannomas. Diagnostic evidence vs. surgery].

+-f having vestibular schwannoma (VS) was conducted in a series of 123 patients (127 tumours), over a 20 year-period from 1973 to 1993. Mean follow up period was 3.4 years, mean annual growth rate was 3.2 mm/year. Tumour growth was observed in 90 patients (94 tumours, 74%), no growth was seen in 23 patients (23 tumours, 18%) and negative tumour growth in 10 patients (10 tumours, 8%). Surgery due to tumour growth was performed in 35 patients (35 tumours, 28%). Seven patients (seven tumours, 6%) were treated with gamma radiation and/or shunt insertion. Seven patients (6%) died of brainstem herniation induced by tumour compression. Nine patients (7%) died of non tumour related causes. Twenty-eight patients were classified as candidates for hearing preservation surgery and 21 patients (75%) lost their candidature during the observation period due to tumour growth and/or deterioration of hearing. The results may limit indications for allocation of patients with VS to the "wait and see" group.

Adolescent↗
PubMed1995

Acoustic neuroma (vestibular schwannoma): growth and surgical and nonsurgical consequences of the wait-and-see policy.

A prospective study of the consequences of the wait-and-see policy in in patients with neuroradiologic diagnostic evidence of having vestibular schwannoma was conducted in a series of 123 patients (127 tumors) over a 20-year period, from 1973 to 1993. The mean follow-up period was 3.4 years, mean annual growth rate was 3.2 mm/year, mean annual volume growth rate was 0.72 ml/year, and mean annual relative growth rate was 41%. Tumor growth was observed in 90 (74%) patients (94 tumors), no growth was seen in 23 (18%) patients (23 tumors), and negative tumor growth was seen in 10 (8%) patients (10 tumors). Surgery due to tumor growth was performed in 35 (28%) patients (35 tumors), 7 (6%) patients (7 tumors) were treated with gamma-radiation and/or shunt insertion, 7 (6%) patients died of brain stem herniation induced by tumor compression, 9 (7%) patients died of non-tumor-related causes, 28 patients were classified as candidates for hearing preservation surgery, and 21 (75%) patients lost their candidacy during the observation period due to tumor growth and/or deterioration of hearing. The results may limit indications for allocation of patients with vestibular schwannoma to the wait-and-see group.

Adolescent↗
PubMed1995

Hyperprolactinaemia in patients with pituitary adenomas. The pituitary stalk compression syndrome.

Hyperprolactinaemia, unexplained by prolactin-production of the tumour is occasionally found in patients with pituitary tumours. This secondary hyperprolactinaemia has been ascribed to a mass effect of the tumour upon the pituitary stalk, obstructing the normal inhibitory hypothalamic influence on the prolactin producing cells. In this study the adenoma volume, amount of suprasellar enlargement of the tumour and the intrasellar pressure were measured in 42 patients operated upon consecutively for pituitary tumours. Secondary hyperprolactinaemia was found in six (14%). There was no difference as regards adenoma volume, amount of suprasellar extension or intrasellar pressure between the group of patients with elevated p-prolactin versus the group with normal p-prolactin. We conclude that mechanisms other than pituitary stalk compression must be considered as the cause of secondary hyperprolactinaemia.

Adenoma↗
PubMed1994

Quantitation of peritumoural oedema and the effect of steroids using NMR-relaxation time imaging and blood-brain barrier analysis.

A new method of in vivo quantitation of peritumoural brain oedema using NMR relaxation time imaging (T1-maps) and Gd-DTPA-enhanced Blood-Tumour-Barrier (BTB) analysis is presented. The method is based on image pixel histogram analysis and a fast imaging method combined with arterial [Gd-DTPA]-measurement. The method was applied in 26 brain tumour patients, studied prior to--and 1, 3 and 7 days after initiation of dexamethasone. Oedema resorption rate following dexamethasone treatment was almost equal in glioblastomas and metastases, mean T1 being reduced by ca. 12% in 7 days. In meningiomas no significant changes in peritumoural oedema could be detected. Simultaneous BTB-analysis was obtained in 4 patients showing correlation between oedema resorption in vivo and reduction of BTB transport rate constant Ki after 7 days of steroid treatment. This method is a powerful tool in quantitation and monitoring of brain oedema in vivo, as both steroid influence on oedema resorption and on BTB-defect can be monitored simultaneously.

Blood-Brain Barrier↗
PubMed1994

Effect of stable xenon inhalation on intracranial pressure during measurement of cerebral blood flow in head injury.

Xenon-enhanced computerized tomography (CT) is well suited for measurements of cerebral blood flow (CBF) in head-injured patients. Previous studies indicated divergent results on whether inhalation of xenon may cause a clinically relevant increase in intracranial pressure (ICP). The authors employed Xe-enhanced CT/CBF measurements to study the effect of 20 minutes of inhalation of 33% xenon in oxygen on ICP, cerebral perfusion pressure (CPP), and arteriovenous oxygen difference (AVDO2) in 13 patients 3 days (mean 1 to 5 days) after severe head injury (Glasgow Coma Scale score < or = 7). The patients were moderately hyperventilated (mean PaCO2 4.3 kPa or 32.3 mm Hg). Six patients were studied before and during additional hyperventilation. All 13 patients reacted with an increase in ICP and 11 with a decrease in CPP. The mean ICP increment was 6.9 +/- 7.7 (range 2 to 17 mm Hg). The mean CPP decrement was -9.7 +/- -14.6 (range 17 to 47 mm Hg). The time course of the ICP changes indicated that ICP increased rapidly during the first 5 to 6 minutes, then declined to a plateau (peak-plateau type in four of 13 patients), remained at a plateau (plateau type in six of 13), or continued to increase in three of 13, indicating individual variance in xenon reactivity. Additional hyperventilation had no effect on the xenon-induced increments in ICP but these occurred at lower ICP and higher CPP baseline levels. The AVDO2 values, an index of flow in relation to metabolism, indicated a complex effect of xenon on CBF as well as on metabolism. This study indicates that xenon inhalation for Xe-CT CBF measurements in head-injured patients according to our protocol causes clinically significant increments in ICP and decrements in CPP. It is suggested that the effect of xenon is analogous to anesthesia induction. Individual variations were observed indicating possible individual tolerance, possible influence of type and extent of the cerebral injury, disturbances in cerebrovascular reactivity, and possible influence of medication. These effects of xenon suggest that hyperventilation should be ensured in patients with evidence of reduced compliance or high ICP. On the other hand, inhalation of stable xenon is not believed to pose a risk because no signs of cerebral oligemia or ischemia were indicated in the AVDO2 values.

Administration, Inhalation↗
PubMed1993

Resorption of peritumoural oedema in cerebral gliomas during dexamethasone treatment evaluated by NMR relaxation time imaging.

Peritumoural brain oedema is a prominent feature of malignant brain tumours. Glucocorticoids diminish the neurological symptoms and signs caused by the oedema and reduce the abnormally high cerebral water content. The exact mechanisms of action of the glucocorticoids are unknown. The present study investigates the influence of dexamethasone on NMR relaxation time T1 in peritumoural oedema in 13 patients with gliomas. It is shown that NMR T1 images can be used as a potent monitor of brain oedema, and that dexamethasone significantly reduces mean T1 after 1, 3, and 7 days of treatment by 2%, 6%, and 13% respectively. Using an image histogram analysis technique the term "super-oedema" was defined as the 50% of the total oedema area with the highest T1, corresponding to the highest water content. It is shown, that with this technique the treatment effect of steroids on super-oedema was a reduction of 13%, 33%, and 57% after 1, 3, and 7 days of treatment respectively. The mean change after 24 hours of treatment was statistically significant (p < 0.01). The method can be used in all situations where the anti-oedematous effect of a given treatment is to be monitored.

Aged↗
PubMed1990

Spiculated vertebral metastases from prostatic carcinoma. Report of first two cases.

Periosteal reaction with spicule formation is very rare in metastatic bone disease, as only 75 cases are reported in the literature. Although prostatic cancer often metastasizes to the spine, spiculation here has not been reported. We present the first two cases of vertebral metastases from prostatic carcinoma with spicule formation giving rise to osseous spinal stenosis and neurological deficits, best demonstrated by CT.

Adenocarcinoma↗
PubMed1990

Cervical analgesic facet joint arthrography.

We report on our experience with cervical analgesic facet joint arthrography in 11 patients (30 joints), of whom nine had previous spinal surgery. In this type of patient we have found the procedure to be a diagnostic test as well as a preoperative guide to the neurosurgeon, but not a permanent therapy.

Adult↗
PubMed1989

Echocardiography and cerebral computed tomography in chronic atrial fibrillation.

Chronic atrial fibrillation (CAF) may be complicated by asymptomatic small silent cerebral infarctions as well as by stroke. The echocardiographic findings in 29 patients with CAF and 29 controls in sinus rhythm are presented. The cerebral computed tomography (CT) findings in these patients were previously published and significantly more small low-density lesions, probably reflecting previous infarctions, were found in patients with CAF than in controls. The aim of the present study was to evaluate if patients with such cerebral lesions had characteristic echocardiographic abnormalities with special reference to patients with CAF. No significant differences could be detected between the groups with and without cerebral lesions regarding the occurrence of valvular heart disease, left ventricular dysfunction, end-diastolic diameter of the left ventricle, left atrial dimension and left ventricular fractional shortening. Only seven patients with CAF (24%) compared with 21 in sinus rhythm (72%) had normal echocardiograms (P less than 0.001). In conclusion, echocardiography gave no guidance to why some patients developed cerebral low-density areas on CT.

Aged↗
PubMed1989

Cerebral ventricular enlargement relates to neuropsychological measures in unselected AIDS patients.

In a cross-sectional study of unselected Danish AIDS patients various linear measures of cerebral ventricular size obtained by computed tomography were compared with results of neuropsychological test performances. Third ventricular width as well as right and left septum-caudate distances were enlarged in the patients (P less than 0.01). Of 20 patients 15 had at least one abnormal ventricular measurement. Although only one patient was demented, ventricular size correlated inversely with neuropsychological function (r = -0.61, P less than 0.02). The correlation between ventricular size and variation of the reaction time was even closer (r = 0.74, P less than 0.01). It is concluded that neuroradiological signs of central atrophy often occur in AIDS patients.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Myelopathy in AIDS. A clinical and electrophysiological study of 23 Danish patients.

In a cross-sectional population study of Danish patients with AIDS 16 of 23 had clinical signs of neurological disease with muscle weakness or ataxia of the lower limbs as the dominant manifestation. Tibial and median nerve conduction was mildly slowed in a few patients and 15 had widening of cerebral ventricles at CT. However, all had prolonged latency of cortical evoked response following tibial nerve stimulation mainly due to slowing through the spinal cord. The prolongation of the latency of the evoked cortical responses was most pronounced in patients with lower limb ataxia and/or paresis. It is concluded that affection of the long tracts of the spinal cord are closely associated with the human immunodeficiency virus infection.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Mixed solvent exposure and organic brain damage. A study of painters.

In recent years, the possible role of occupational solvent exposure as a cause of chronic effects on the brain has been a matter of increasing concern. The present study was undertaken with the purpose of further investigating this problem, trying to minimize confounding owing to effects of recent solvent exposure and a 'healthy worker' effect. This was accomplished by studying a historical cohort of painters. The material consists of a random sample of 85 painters, and as a non-exposed control group of 85 bricklayers, selected in the same way. Parts of the study are based on this sample supplemented by a sample of 9 painters and 14 bricklayers, selected among subjects with a high degree of complaints on mental impairment. On the basis of a detailed interview on previous solvent exposure, the painters were divided into three groups with low, medium and high solvent exposure, respectively. As signs of organic brain damage we used the degree of dementia and performance in psychometric tests as assessed at a neuropsychological examination; the degree of dyscoordination as assessed from clinical neurological tests; and the degree of cerebral atrophy as assessed from CT-scans of the brain. CT-scans were performed only on a specially selected subsample. The degree of dementia, dyscoordination, and cerebral atrophy increased significantly with the degree of solvent exposure. A similar, but non-significant association was found for the relation between performance in psychometric tests and solvent exposure. The degree of dementia, of dyscoordination, and of cerebral atrophy were positively associated with each other, suggesting that they reflect different aspects of a common underlying factor, an organic brain damage. A review of the literature compared with the results of the present study suggests that a number of studies may have been biased towards negative findings owing to the inclusion in the study material of large proportions of subjects with a solvent exposure that is too little to increase the risk of an organic brain damage. Conflicting results between different studies on performance in psychometric tests may also arise from insufficient adjustment for primary intellectual level.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1986

Lumbar disc disease evaluated by myelography and postmyelography spinal computed tomography.

Five- and ten-millimeter-thick transverse axial computed tomography (CT) scans were obtained at lumbar disc spaces in 81 patients with suspected lumbar disc disease. Scans were obtained following metrizamide myelography. CT and myelography findings were compared and correlated with clinical and surgical findings. Postmyelography CT scan was superior to myelography in 68% since it was able to demonstrate even small herniations. It was especially valuable in the L5-S1 space where the wide epidural space can hide the disc herniation without it being demonstrated by myelography. Also other kinds of pathology which may simulate or complicate disc herniation were readily evaluated by postmyelography CT. Although noncontrast CT scans are usually diagnostic and sufficient, the improved anatomical details obtained by postcontrast CT scans, increase the diagnostic accuracy, and selected, complicated cases may need the CT study with intrathecal metrizamide.

Adult↗