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Biomedical subjects

O Smedby

Publications and source records attributed to O Smedby.

36 records · Page 2Linked to original sources
PubMed1996

Anatomical variations of the human vestibular aqueduct. Part I. A radioanatomical study.

Variations in the size and shape of the human vestibular aqueduct were evaluated in 118 plastic casts of unselected specimens of human temporal bones. They were examined by conventional radiography and by high resolution CT. The degree of the mastoid and perilabyrinthine pneumatization was defined and classified into 3 types. The dimensions of the peripheral portion of the aqueduct were found to be related to the extent of the perilabyrinthine pneumatization.

Humans↗
PubMed1996

Anatomical variations of the human vestibular aqueduct. Part II. A radioanatomical study.

The human vestibular aqueducts are classified into 3 types and into the types hyper-, normo- and hypoplastic. The types correspond with each other up to over 85%. For a better understanding of the radioanatomy and for the proper interpretation of radiograms, we describe the presence of a flat recess-like widening of the peripheral portion of the aqueduct, as well as other findings.

Humans↗
PubMed1996

Anatomical variations of the tympanic and mastoid portions of the facial nerve canal. A radioanatomical investigation.

PURPOSE: To obtain information on the morphology of the tympanic and mastoid portions of the facial nerve canal, and on the appearance of unusual vascular channels and anomalies such as dehiscences. MATERIAL AND METHODS: One hundred and two temporal bone preparations were examined by conventional radiography to evaluate mastoid pneumatization. Of these, 73 were examined by high resolution CT in order to test the ability of the method to detect dehiscences in the bony wall of the tympanic portion of the canal and the accompanying channels along its mastoid portion. Subsequently produced plastic preparations were used to measure the length and width of these 2 portions of the facial canal. RESULTS: Our study reports observations on the three-dimensional morphology of the canal in the plastic casts. The study shows variations in the course and dehiscences of the tympanic portion. Additional bony channels along the mastoid portion are described. These results supplement those in previous investigations. CONCLUSION: The measurement results agree with those of previous investigations. The course of the tympanic portion is S-shaped and has an impression on its upper surface. High resolution CT reproduces dehiscences of the bony canal in a percentage similar to that of microscopical methods and in relevant sites. Pneumatization does not influence the dimensions of the 2 portions.

Ear, Middle↗
PubMed1995

Predilection of atherosclerosis for the inner curvature in the femoral artery. A digitized angiography study.

The degree of atherosclerosis in the inner and outer curvature of the femoral artery was studied by using digitized angiography and edge-roughness calculations in 301 hyperlipidemic patients. When the two edges of the vessel were compared no significant difference was seen, but when the local curvature was taken into account, inner curves were found to be more atherosclerotic than outer curves, and both inner and outer curves were more affected than straight segments. The same pattern was encountered in subpopulations defined by clinical or blood lipid criteria. The suggested explanation is that flow disturbances such as low shear rates or separated flow, which tend to arise along the inner curvature, promote the development of atherosclerosis.

Adult↗
PubMed1993

Flow disturbances in early femoral atherosclerosis--an in vivo study with digitized cineangiography.

Disturbances in arterial flow are believed to influence the localization and development of atherosclerotic plaques. The femoral arteries of 26 patients were studied with cineangiography, after which the films were digitized and analyzed with an image analysis computer. The image sequence was converted to a set of time-intensity curves, from which time parameters were calculated, representing the arrival time of the contrast medium at each pixel. In the resulting parametric images, zones of delayed contrast filling (ZDF) were identified by an adaptive thresholding, which identifies lighter regions within the vessel, excluding the smallest ones. The ZDF, which have been shown, in a model study, to correspond to disturbed flow, were more frequent in the inner curvature than in the outer curvature of the curved vessels. Accordingly, they were more frequent along the lateral wall than along the medial wall of the artery. Several ZDF were also found in the vicinity of bifurcations. Most of the findings tally closely with fluid mechanical theory. In future studies, flow disturbances are to be correlated with the progression of atherosclerotic lesions.

Adult↗
PubMed1992

Angiographic methods for the study of fluid mechanical factors in atherogenesis.

The purpose of this thesis is to investigate the feasibility of using angiographic methods to study, in vivo, fluid mechanical phenomena believed to influence the development and localization of atherosclerotic lesions, in particular, separated flow. This involved developing a method to recognize separated flow by digital analysis of cineangiography films, testing this method both with model measurements and in a clinical material, and a detailed analysis of certain methodological problems. In addition, methods have been developed to measure the tortuosity of arteries, a phenomenon which may, according to fluid mechanical theory, promote the occurrence of separated flow. In a glass model of an arterial bifurcation, a pump generated a pulsatile flow resembling that in large arteries. Using LDV (laser Doppler velocimetry) as a reference method, three velocity profiles in the symmetry plane of the model were recorded. During diastole, extensive separated flow was demonstrated in the larger branch of the bifurcation. The flow was then cineradiographed during injection of contrast medium, and the image sequence was transferred to an image analysis workstation. Treating the image sequence as a set of time-intensity curves, time parameters representing the arrival time of the contrast agent were computed. In the resulting parametric images, zones of delayed filling were identified and found to correspond to the separated flow. Viscosity was measured for seven radiographic contrast media and, as expected, the highest values were found for the largest molecules. For iohexol and ioxaglate, which were studied in detail, a linear relation to temperature and a quadratic relation to concentration were found. Whole-blood viscosity was measured for 5 healthy volunteers at high and low shear rates, before and after mixing with contrast agents in varying proportions. At low shear, viscosity decreased, while at high shear, it increased with increasing contrast concentration. The conclusion was that modern contrast media, despite their higher viscosity, seem to affect blood rheology less than older agents. In a study of the imaging characteristics of the digitization equipment for cinefilms, the resolution proved comparable to that of an entirely digital system, while the noise level was higher. Algorithms for the correction of variations in exposure and geometric distortion are also presented. The method for analysis of cinefilms, tried in the model study, was applied, with slight modifications, to a material of 26 patients with hyperlipidemia and slight or moderate atherosclerosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Viscosity of some contemporary contrast media before and after mixing with whole blood.

The viscosity of 7 contrast media was measured using a rotational viscometer. When solutions with similar iodine concentrations were compared, the highest viscosities were found for the nonionic dimers iodixanol and iotrolan, the lowest for diatrizoate, iopamidol, and iopromide, and intermediate values for iohexol and ioxaglate. The viscosity of iohexol and ioxaglate was found to vary linearly with temperature and quadratically with concentration. Whole-blood viscosity was measured for 5 subjects at high and low shear rates before and after mixing with contrast media in various proportions. Low-shear viscosity was found to decrease and high-shear viscosity to increase with contrast medium concentration. It is concluded that the contrast media currently used may affect blood rheology less than previous agents, despite their higher viscosity.

Adult↗
PubMed1991

Separated flow demonstrated by digitized cineangiography compared with LDV.

In order to demonstrate separated flow in vivo, a method for the computerized analysis of cineangiographies has been developed, tested in vitro, and compared with LDV. A pulsatile flow was created in a glass model bifurcation, and velocity profiles were obtained with LDV at several phase angles. The flow was cinefilmed during contrast injection and the images were digitized. The computer then transformed the image sequence into parametric images representing arrival times of the contrast. The separation regions demonstrated with LDV were identified as areas with delayed contrast arrival. A preliminary analysis of a cineangiography in vivo is also included.

Arteries↗
PubMed1990

Assessment of congestive heart failure in chest radiographs. Observer performance with two common film-screen systems.

The effect of observer variations and film-screen quality on the diagnosis of congestive heart failure based on chest radiographs was studied in 27 patients. For each patient, two films were exposed, one with the Kodak Lanex Medium system and one with the Agfa MR 400 system. The films were presented to three observers who assessed the presence of congestive heart failure on a three-graded scale. The results showed no significant difference between the two systems but large systematic differences between the observers. There were also differences between the two ratings by the same observer that could not be explained by the film-screen factor. It is concluded that the choice between these two systems is of little importance in view of the interobserver and intraobserver variability that can exist within the same department.

Heart Failure↗
PubMed1986

Measures of continuity of care. A register-based correlation study.

In an empirical study using data from a health center in Sweden, correlation coefficients were computed among nine different measures of continuity of care, five of them visit-based and four individual-based. Generally, the correlations were high. This may be due, in part, to the similar behavior of the measures for people making few visits. The correlations were also quite high, however, when the sample was restricted to people with many visits. Several measures display a significant dependence on utilization level. The results suggest that, for general purposes, the measure COC should be preferred among the individual-based measures and fraction-of-care continuity among the visit-based measures. On grounds of flexibility and ease of interpretation, the authors recommend fraction-of-care measures.

Continuity of Patient Care↗
PubMedDate not supplied

Tortuosity and atherosclerosis in the femoral artery: what is cause and what is effect?

Earlier studies have demonstrated a correlation between tortuosity and atherosclerosis in the femoral artery. One conceivable explanation is that atherosclerosis causes an elongation of the artery, resulting in vessel tortuosity, another is that blood flow phenomena (such as flow separation) due to the vessel geometry may affect the progression of atherosclerosis. To determine which of these hypotheses is most likely, a group of 232 hyperlipidemic patients was followed with angiography for 3 years during lipid-lowering treatment. After digitization of the films, a tortuosity value and an atherosclerosis measure (edge roughness) were computed. In the group with lower tortuosity values, there was a significant (p < 0.0001) decrease in edge roughness, but not in the group with a higher tortuosity values. On the other hand, neither the group with higher edge roughness values nor that with lower edge roughness values displayed a significant change in tortuosity. When tortuosity, roughness, and treatment were studied simultaneously, only the effect of tortuosity on roughness change was significant. These findings are more consistent with tortuosity influencing the development of atherosclerosis than with its being a consequence of atherosclerosis.

Adult↗
PubMedDate not supplied

Geometric risk factors for atherosclerosis in the aortic bifurcation: a digitized angiography study.

To clarify the relationship between arterial geometry and atherosclerosis at the aortic bifurcation, angiograms of 84 patients with slight or moderate atherosclerosis were studied by computerized image analysis. The degree of atherosclerosis involvement was assessed as angiographic edge roughness. The branching angles were found to be related to edge roughness of the left outer wall and the right side of the aorta. The position of the flow divider was related to edge roughness of the medial wall of the right common iliac and the right side of the aorta. For these two locations, there were also significant relationships to the area ratio, i.e., the ratio between cross-sectional areas distal and proximal to the bifurcations. On the basis of these findings, the concept of "geometric risk factors" for atherosclerosis and the potential influence of blood flow on atherogenesis are discussed.

Adult↗
PubMedDate not supplied

A scanning system for digital analysis of cineangiography films.

A system for scanning and digital analysis of cinefilms is presented and its performance is compared with entirely digital radiographic equipment. Apart from the difference between logarithmic and linear gray-scale representation, a higher noise level was found in the scanning system. When its spatial resolution was assessed visually, it was comparable to that of the digital system, although lower than when the cinefilming and scanning steps were evaluated separately. Algorithms for the correction of varying exposure and geometric ("pin-cushion") distortion are also presented. It is concluded that digital analysis after scanning of cinefilms can be a useful alternative to completely digital cineradiographic studies.

Algorithms↗
PubMedDate not supplied

Geometrical risk factors for atherosclerosis in the femoral artery: a longitudinal angiographic study.

In order to study the evolution of atherosclerosis in the superficial femoral artery in relation to local factors of vascular geometry, image processing of digitized angiograms was carried out in 237 hyperlipidemic patients before and after a three-year period of lipid-lowering treatment. The degree of atherosclerosis was measured as edge roughness, which was calculated separately for inner curves, outer curves, and straight segments and, in a subgroup of 110 patients, for segments with and without branches on either side of the artery. Initially, inner curves had significantly higher roughness values than outer curves, and outer curves higher than straight segments. After three years, there was an increase of borderline significance in the outer curves, and the difference between inner and outer curves was no longer significant. In several subpopulations, the increase in outer curve roughness was clearly significant. When branched and nonbranched segments were compared, the only significant difference was at the second examination where segments with a lateral branch had higher roughness of the medial edge than those without such a branch. It is concluded that curves are more likely than bifurcations to constitute a geometric risk factor for atherosclerosis, but it remains to explain the causal mechanism for this factor.

Adult↗
PubMedDate not supplied

Two-dimensional tortuosity of the superficial femoral artery in early atherosclerosis.

Tortuosity of an artery can disturb fluid mechanics and cause flow separation, which might in turn promote atherogenesis. This study discusses theoretically several quantitative measures of arterial tortuosity and curvature in two dimensions and tests them with computations from digitized femoral arteriograms. When reproducibility, sensitivity to scaling and computational procedure, and agreement between the measures were all taken into account, the total curvature and distance factor were considered the most suitable measures. Significant correlations were found between tortuosity and atherosclerosis measures, but the interpretation of this finding is not straightforward.

Aged↗