Biomedical subjects

C R Mol

Publications and source records attributed to C R Mol.

6 recordsLinked to original sources

PubMed1986

Three-dimensional graphics display of X-ray angiography data.

A method for making three-dimensional computer graphics displays of in vivo blood vessels is described. Input data are taken from biplane X-ray angiograms using an image-processing system. A display list is built up which is then sent to a high-function graphics system. Real-time interaction is possible using a vector-refresh display where the blood vessel segments are shown as cylinders of the appropriate diameter. Realistic raster representations may be used to give the user insight into the overall topology of the network of vessels. The Winchester Graphics System is described together with explanations of the techniques employed.

Angiography↗

PubMed1984

A computer-aided method to evaluate the function of implanted Björk-Shiley prosthetic heart valves.

Evaluation of the function of implanted prosthetic valves is important in early diagnosis of valve dysfunction. Björk-Shiley valves contain two radiopaque rings, which are projected as ellipses in cineradiography. From these ellipses the actual valve opening angle can be calculated. A computer-aided method was developed that enables measurement of ellipse characteristics reliably, independent of projection angle and valve opening. It is demonstrated that calculated and real opening angles differ less than 2 degrees with this method. Using the same technique the tilting angle of the valve ring during the cardiac cycle is computed for evaluation of progression of valve dehiscense in case of a paravalvular leak. Application of the method to patient data is illustrated by three cases. The method is suitable for use by technicians. It can be implemented on a small microprocessor system. The method proved to be a powerful tool in the evaluation of patients with implanted Björk-Shiley valves.

Aortic Valve↗

PubMed1982

Ultrasound velocity in muscle.

Measurements are reported on the propagation velocity of ultrasound in muscle tissue. This appears to be dependent on fiber direction for various muscle types (in vitro). Typical results are 1550 m/s perpendicular and 1557 m/s parallel to fiber direction (20 degrees C). A model is drawn up to relate such data to the elastic properties of muscle. It is shown that the assumptions: linear elastic behavior, homogeneity, and anisotropy with cylindrical symmetry, do not harmonize with the experimental results. A more elaborate model is suggested. Contraction dependence of the ultrasound velocity was investigated on human biceps muscle (in vivo) and frog gastrognemius muscle (in vitro). The measured velocity increase in biceps muscle during contraction--up to 3 m/s--is attributed to a varying blood content of the muscle. In (in vitro) frog muscle contraction is not accompanied by a change in ultrasound velocity. This suggests that increased muscle stiffness is not appreciably reflected in ultrasound velocity.

Animals↗

PubMed1982

Cardiac function, fiber shortening, and dynamic geometry.

Many models for the study of the pump function of the heart emphasize the importance of cardiac geometry and detailed dimensional data. Because of the lack of accurate measuring techniques, approximate geometries such as shells of revolution have been applied. In this study, methods are presented that measure the dynamic geometry of the working, isolated canine heart by means of ultrasound-velocity tomography techniques. In addition, cardiac dimensions, intramural deformations, and fiber shortening have been measured dynamically in the in situ canine heart throughout the cardiac cycle with implanted radiopaque markers and biplane roentgen techniques. Results of regional contraction and relaxation patterns are presented. Epicardial fiber shortening between apex and base were computed and found to be dependent on the duration of the preceding RR interval.

Animals↗

PubMed1981

Ultrasound velocity tomography, an imaging method.

Analysis of the geometry of the beating heart may yield important information about its condition and function, and may reveal physiologically and clinically relevant information about the influence of regional malfunctioning on the integral heart performance. In this study, a method has been developed which will ultimately allow the determination of the three-dimensional geometry of an isolated working dog-heart throughout the cardiac cycle. The technique will be called 'ultrasound velocity tomography'. Ultrasound velocity tomograms are reconstructions of the spatial distribution of the ultrasound velocity in cross-sections of the object under study. This velocity is to a certain extent characteristic for a tissue, so that various tissues and structures can be identified in a tomogram. The velocities are mathematically reconstructed from thousands of measured times-of-flight of ultrasound pulses which have travelled along different path-ways through the object. By detecting the blood-heart muscle transitions in a tomogram and by combining tomograms from different cross-sections of the heart, a three-dimensional heart-geometry may be obtained. Preliminary results on a formalin-fixed heart are shown and discussed.

Animals↗

PubMed1977

A quantitative assay of cortisol in human plasma by high performance liquid chromatography using a selective chemically bonded stationary phase.

The extraction and subsequent liquid chromatographic analysis of human plasma samples for cortisol is described. Extraction and chromatography are optimized, resulting in a recovery for cortisol of 96% and a detection limit of 1 microgram cortisol in 100 ml plasma. The application of two chemically modified silicas has been evaluated. The specificity of the method was tested by field desorption - mass spectrometry experiments.

Chromatography, High Pressure Liquid↗