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Biomedical subjects

T Gustavsson

Publications and source records attributed to T Gustavsson.

At least 19 recordsLinked to original sources
PubMed2003

Rotational diffusion of the 7-diethylamino-4-methylcoumarin C1 dye molecule in polar protic and aprotic solvents.

Fluorescence anisotropy decays of the 7-diethylamino-4-methylcoumarin C1 in various polar solvents of different viscosities and hydrogen bond donor/acceptor character have been recorded by means of the fluorescence upconversion and time-correlated single photon counting techniques. The resulting characteristic times for the rotational diffusion fall into two classes with regards to the viscosity-dependency: n-alcohols and "other" solvents. This deviation from the simple Stokes-Einstein-Debye model may be interpreted in terms of rotation of the coumarin molecule under two different hydrodynamic boundary-conditions ("stick" or "slip") in the two solvent classes. Possible explanations for this behaviour are discussed, and in particular solvent attachment and additional dielectric friction. Both these phenomena may in fact, under certain conditions, explain our findings. Our opinion, however, is that the dielectric friction model offers a more realistic picture of the additional rotational friction experienced by C1 in n-alcohols.

Journal Article↗
PubMed2000

A multiscale dynamic programming procedure for boundary detection in ultrasonic artery images.

Ultrasonic measurements of human carotid and femoral artery walls are conventionally obtained by manually tracing interfaces between tissue layers. The drawbacks of this method are the interobserver variability and inefficiency. In this paper, we present a new automated method which reduces these problems. By applying a multiscale dynamic programming (DP) algorithm, approximate vessel wall positions are first estimated in a coarse-scale image, which then guide the detection of the boundaries in a fine-scale image. In both cases, DP is used for finding a global optimum for a cost function. The cost function is a weighted sum of terms, in fuzzy expression forms, representing image features and geometrical characteristics of the vessel interfaces. The weights are adjusted by a training procedure using human expert tracings. Operator interventions, if needed, also take effect under the framework of global optimality. This reduces the amount of human intervention and, hence, variability due to subjectiveness. By incorporating human knowledge and experience, the algorithm becomes more robust. A thorough evaluation of the method in the clinical environment shows that interobserver variability is evidently decreased and so is the overall analysis time. We conclude that the automated procedure can replace the manual procedure and leads to an improved performance.

Carotid Artery, Common↗
PubMed1999

Single-cell volume estimation by three-dimensional wide-field microscopy applied to astroglial primary cultures.

Astrocytes, which constitute a prominent part of the number and volume of brain cells, have a high capacity for controlling their volume, and astrocytic swelling is associated with a number of pathological states affecting the CNS. In order to understand the mechanisms for regulating cell volume in astrocytes better, it is of utmost importance to develop technical instrumentation and analysis methods capable of detecting and characterizing dynamic cell shape changes in a quantitative and robust way. For this purpose, a new method was developed to quantify changes in cell volume at the single-cell level. This method is based on three-dimensional (3D) fluorescence imaging obtained by optical sectioning. An automated image acquisition system was developed for the collection of two-dimensional (2D) microscopic images. A deblurring algorithm was implemented in order to restore the originally unfocused image content. Advanced image analysis techniques were applied for accurate and automated determination of cell volume. The sensitivity and reproducibility of the method was evaluated by using fluorescent beads. The techniques were applied to fura-2-labeled astroglial cells in primary culture exposed to hypo- or hyperosmotic stress. The results show that this method is valuable for determining volume changes in cells or parts thereof.

Animals↗
PubMed1998

Assessment of facial features with a range camera.

We describe a new method for the quantitative analysis of facial features using a range camera with a three-dimensional measuring program. The range camera consists of a video camera, a light projector, and a computer. The video camera captures a number of images of different light patterns projected on to the face. From these, a "range image" is computed. One fully illuminated intensity image of the face is also taken. By defining anatomical landmarks manually on the intensity image, three-dimensional measurements are automatically obtained from corresponding positions in the range image. The method is highly accurate and precise, and is a simple and reliable way of assessing facial features. We recommend that the system be adapted in clinical practice--for example, in diagnosing syndromes and planning plastic and reconstructive surgery.

Cephalometry↗
PubMed1997

Effects of halothane and isoflurane on left ventricular diastolic function during surgical stress in patients with coronary artery disease.

BACKGROUND: The effects of inhalation anesthetics on left ventricular (LV) systolic function are well documented, while the effects of these agents on LV diastolic function have mainly been evaluated in animal studies, with conflicting results. METHODS: We investigated the effects of halothane and isoflurane, when used to control the stress response to sternotomy in 33 patients with coronary artery disease (CAD). LV early diastolic relaxation and end-diastolic stiffness were evaluated from mitral Doppler flow profiles, transesophageal two-dimensional echocardiography, and central hemodynamic measurements. Measurements were performed a) after induction of anesthesia, b) after volume loading, c) prior to surgery and d) during surgery, 10 min after introduction of the inhalation anesthetic. The effects of the anesthetics on Doppler indices reflecting early diastolic relaxation, and on the left ventricular end-diastolic pressure-area (LVED P/A) relationship, were studied. RESULTS: When data obtained during surgical stress were compared to the control situation, we found an increase in the LV filling pressures in both groups, while only the isoflurane group showed an increase in heart rate. An increase in end-systolic LV area and decreased fractional area change was present in the halothane group, while an increase in LV end-diastolic area, and similar changes in the mitral Doppler indices (decreases of deceleration rate and time of early diastolic filling), indicating an impairment of early diastolic relaxation, was present in both groups. Isoflurane induced a displacement of the LVED P/A relationship leftwards from the baseline LVED P/A curve. CONCLUSION: Both halothane and isoflurane impair early diastolic relaxation in patients with CAD, when used to control intraoperative surgical stress. In contrast to halothane, isoflurane induced a change in the LVED P/A relationship, suggestive of an increased LVED stiffness.

Adult↗
PubMed1997

A new automated computerized analyzing system simplifies readings and reduces the variability in ultrasound measurement of intima-media thickness.

BACKGROUND AND PURPOSE: A computerized analyzing system with manual tracing of echo interfaces for measurement of intima-media thickness and lumen diameter in carotid and femoral arteries was previously developed by our research group and has been used for many years in several laboratories. However, manual measurements are not only time consuming, but the results from these readings are also dependent on training and subjective judgement. A further problem is the observed drift in measurements over time. A new computerized technique for automatic detection of echo interfaces was therefore developed. The aim of this study was to evaluate the new automated computerized analyzing system. METHODS: The new system is based on dynamic programming and includes optional interactive modification by the human operator. Local measurements of vessel echo intensity, intensity gradient, and boundary continuity are extracted by image analysis techniques and included as weighed terms in a cost function. The dynamic programming procedure is used for determining the optimal location of the vessel interfaces in a way that the cost function is minimized. RESULTS: With the new automated computerized analyzing system the measurement results were less dependent on the reader's experience, and the variability between readers was less compared with the old manual analyzing system. The measurements were also less time consuming. CONCLUSIONS: The new automated analyzing system will not only greatly increase the speed of measurements but also reduce the variability between readers. It should also reduce the variability between different laboratories if the same analyzing program is used. Furthermore, the new system will probably prevent the problem with drift in measurements over time.

Automation↗
PubMed1995

Morphometry of the optic nerve and retinal vessels in children by computer-assisted image analysis of fundus photographs.

BACKGROUND: The retinal fundus in childhood has a different morphology than in adulthood. Existing methods are not suitable for evaluation of fundus photographs from children. Therefore, a new method for quantitative analysis of fundus morphology utilizing a personal computer-assisted digital mapping system was developed. METHODS: A CCD flatbed scanner is used to digitize fundus photographs, producing computer images which are analyzed on an IBM/AT computer. Area measurements of the optic disc, excavation and peripapillary crescent are made, as well as determinations of the length, branching, tortuosity and distribution of the retinal vessels on the fundus surface. RESULTS: Determination of the inter- and intra-observer variability of the computer-assisted image analysis technique demonstrated good reproducibility. The method is demonstrated using fundus photographs of six normal children and six children with the fetal alcohol syndrome. Typical variations in appearance of optic disc and retinal vessels are seen. CONCLUSION: The system is unique in measuring both the optic nerve head and the retinal vessels and is therefore especially useful for detailed studies of normal and abnormal development of these structures in children.

Adolescent↗
PubMed1995

Use of computer-assisted image analysis for noninvasive evaluation of oral lichenoid reactions and oral leukoplakia.

The objective of the present study was to elaborate and to evaluate a method in which the clinical appearance of a mucosal lesion could be expressed by means of color and morphologic features extracted from digitized images. The ability to express mucosal changes with image features was evaluated, as was the accuracy of a classification of the lesions on the basis of image feature analysis. Computer-assisted image analysis was performed on digitized color slides from 76 patients with lichenoid reactions that included both oral lichen planus and contact lesions and 20 patients with homogenous oral leukoplakia. Color features were measured according to the intensity-hue-saturation color system, and morphologic features were estimated by tracing the hyperkeratotic area. Hyperkeratinizing and inflammatory tissue reactions could be demonstrated and defined by image analysis. Image features indicating inflammatory tissue reactions were more pronounced in cases of oral lichenoid reactions. Morphologic parameters could express the anatomic appearance of the lesions. The comparison between histopathologic diagnosis and a classification through computerized analysis demonstrated that 90.5% of oral lichenoid reactions could be separated from homogenous oral leukoplakia by linear discriminant analysis.

Analog-Digital Conversion↗
PubMed1995

Effects of adenosine infusion on systolic and diastolic left ventricular function after coronary artery bypass surgery: evaluation by computer-assisted quantitative 2-D and Doppler echocardiography.

The effects of adenosine on central hemodynamics, ST-segment changes, and left ventricular (LV) systolic and diastolic function, determined by transesophageal 2-D and Doppler echocardiography, were investigated in 20 patients shortly after coronary surgery. After control measurements, adenosine was infused at incremental infusion rates (30, 60, and 120 micrograms.kg-1.min-1). Adenosine caused dose-dependent increases in heart rate (68.0 +/- 11.2-74.0 +/- 15.7 bpm), cardiac output (3.23 +/- 0.76-4.17 +/- 0.67 L/min), and stroke volume (48.8 +/- 12.5-56.7 L/min), and stroke volume (48.8 +/- 12.5-56.7 mL), decreases in arterial pressure (84.8 +/- 16.6-63.3 +/- 15.2 mm Hg), and systemic and pulmonary vascular resistances (1994 +/- 510-1106 +/- 309 and 209 +/- 54-116 +/- 58 dyne.s.cm-5, respectively), but no changes in cardiac filling pressures. The mean ST segment was slightly but significantly depressed by adenosine (from 0.003 to 0.019 mV). Analysis of LV wall motion showed that adenosine caused no changes in the global area ejection fraction (GAEF), the segmental area ejection fraction (SAEF), or in the SAEF/GAEF ratio, indicating that no regional wall motion abnormalities appeared. Maximum early and late diastolic flow rates (Emax, Amax), determined by mitral Doppler analysis, increased (from 30.1 +/- 14.8 to 40.1 +/- 24.1 and from 37.8 +/- 15.7 to 46.4 +/- 31.3 cm/s, respectively), as did the deceleration slope of the early diastolic filling (from -151 +/- 67 to -210 +/- 107 cm/s-2), whereas no changes were found in the ratio between Emax and Amax, the deceleration time of early diastolic filling, or the velocity time integrals of early or late diastolic filling.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1995

The effects of nitrous oxide on left ventricular systolic and diastolic performance before and after cardiopulmonary bypass: evaluation by computer-assisted two-dimensional and Doppler echocardiography in patients undergoing coronary artery surgery.

We investigated the effects of nitrous oxide (N2O) on central hemodynamics and left ventricular systolic and diastolic function in 25 patients undergoing coronary artery bypass surgery. All patients were receiving beta-blockers and had good left ventricular function. Global and regional systolic left ventricular performance and diastolic function were determined by computer-assisted analysis of transesophageal echocardiographic (TEE) images, and mitral Doppler flow profiles, respectively. The patients were anesthetized with fentanyl and ventilated with oxygen in air. Hemodynamic and TEE measurements were obtained before and after the introduction of N2O in oxygen (60%/40%), before and after cardiopulmonary bypass (CPB). N2O reduced mean arterial pressure, heart rate, stroke volume, and cardiac output both before and after CPB. Left ventricular global area ejection fraction (GAEF) was not changed by the introduction of N2O, either before or after CPB. N2O induced a significant change in regional wall motion after, but not before CPB, as assessed by the relationship between segmental area ejection fraction (SAEF) and GAEF. Analysis of the mitral flow profile indicated an increase in early diastolic relaxation in the pre-CPB period after introduction of N2O, that was absent in the post-CPB period. We conclude that N2O induces regional wall motion abnormalities and possibly diastolic dysfunction post-CPB.

Blood Pressure↗
PubMed1995

Automated correction of linear deformation due to sectioning in serial micrographs.

This paper describes an objective and automatic method for detection and correction of sectioning deformations in digitized micrographs, as well as an evaluation of the method applied to light and electron microscopic images of semi-thin and ultra-thin serial sections from brain cortex. The detection is based on matching of image subregions and the deformation model is bi-linear, i.e. two first-order polynomials are used for modelling compression/expansion in perpendicular directions. The procedure is applicable to prealigned serial two-dimensional sections and is primarily aimed at three-dimensional reconstruction of tissue samples consisting of a large number of cells with random distribution and morphology.

Animals↗
PubMed1995

Image quality in digital chromosome analysis systems.

This paper reports on an investigation into the differences in image quality of different components used in a digital image processing system for chromosome analysis. As chromosome aberrations are important tools in the cloning of genes, it is important to know if the introduction of computerized analysis systems increases the risk of missing small aberrations. In this investigation the number of visible bands on a number of chromosomes has been used as a measure of quality. The images compared are microscope ocular images, photographs from a microscope built-in camera, digital images from a high and from a standard resolution camera, presented both on screen and print-out on paper. The main conclusions are that: (1) the view in the microscope ocular gives the best resolution, (2) there are risks of losing vital information using the digital image processing system for chromosome analysis, and (3) this risk is significantly reduced when using a high resolution camera.

Chromosome Banding↗
PubMed1994

Computer analysis in oral lichenoid reactions.

To improve diagnostic procedures and facilitate clinical decision-making, computer-assisted image analysis was performed on color slides from 30 patients with histopathologically verified oral lichenoid reactions. Areas from white hyperkeratotic and adjacent red inflamed areas of the lesions were selected and subjected to image analysis. The digitization of the color slides was done by means of an image scanner, and the digital information was transmitted to a personal computer for subsequent feature extraction and analysis. The different oral lesions were characterized as the difference in mean values between white hyperkeratotic and red inflamed areas, respectively, compared with clinically normal tissue. Statistical analyses were made on three different color systems: Red-Green-Blue (RGB), normalized red-green-blue (rgb), and Intensity-Hue-Saturation (IHS). The results showed statistically significant differences in all color systems for both the hyperkeratotic areas and adjacent inflammatory reactions. A linear correlation was obtained when the results of the image analysis of color variations were compared with a clinical score system for hyperkeratosis and inflammation evaluated by two investigators independently.

Algorithms↗
PubMed1992

Computer-assisted realignment of light micrograph images from consecutive section series of cat cerebral cortex.

Two computer- and image-analysis-based procedures for realignment of images of consecutive light micrographs of nerve tissue (cat motor cortex) have been developed. One procedure (CENT) was interactive, employing the subjective overall 'best fit' of two images to each other and the other (AUTOCENT) was based on an automatic comparison of two images (image thresholding and binary comparison). Images of light micrographs of several hundred consecutive sections were realigned using the interactive and the automatic methods. The interactive procedure was easy to use; realignment of an image took only a few minutes in the hands of an experienced operator and should be easy to implement on commercially available smaller computers like PCs and workstations, but the realignment was possibly disturbed by the operator's subjective expectancy of regular forms. The automatic procedure realigned 1-4 images per hour, might be implemented on smaller computers if the programming is made more efficient, was probably objective and restored the 'true position of images'.

Animals↗
PubMed1992

Effects of surgical stress and volatile anesthetics on left ventricular global and regional function in patients with coronary artery disease. Evaluation by computer-assisted two-dimensional quantitative transesophageal echocardiography.

We investigated the effects of halothane, enflurane, and isoflurane on central hemodynamics and left ventricular global and regional function when used to control intraoperative hypertension in 39 patients with coronary artery disease. Left ventricular short-axis, midpapillary images were obtained by transesophageal echocardiography. Using a centerline algorithm, we analyzed left ventricular images for global area ejection fraction (GAEF) and segmental area ejection fraction (SAEF). The SAEF/GAEF ratio was calculated for each of eight segments. Measurements were performed after induction of anesthesia but before skin incision; 1 min after sternotomy; and during administration of the inhaled anesthetic. The increase in arterial blood pressure during sternotomy was due to an increase in vascular resistance accompanied by increases in heart rate and filling pressures while GAEF decreased. No changes in the SAEF/GAEF ratio appeared during sternotomy. The inhaled anesthetics restored arterial blood pressure by a similar decrease in vascular resistance. Isoflurane caused an increase in cardiac index that was not seen with halothane or enflurane (halothane vs isoflurane, P < 0.05). The GAEF was decreased by halothane but unaffected by isoflurane and enflurane (halothane vs enflurane; P < 0.05). Isoflurane induced a decrease in the SAEF/GAEF ratios of two segments corresponding to the inferolateral wall of the left ventricle that was, in one of these segments, significantly more pronounced compared with both halothane and enflurane. Halothane or enflurane did not cause any change in regional wall motion. We conclude that isoflurane is more likely to cause regional wall motion changes than halothane or enflurane in patients with coronary artery disease.

Adult↗