Biomedical subjects
W van Damme
Publications and source records attributed to W van Damme.
The distance used for scaling disparities is the same as the one used for scaling retinal size.
To determine the physical size and global three-dimensional (3-D) shape of an object, retinal size and retinal disparity have to be scaled in accordance with the object's distance. We examined whether the distance used for scaling retinal disparity is the same as the distance used for scaling retinal size. Subjects adjusted the 3-D shape (size and depth) of a computer-simulated ellipsoid to match a tennis ball. Analysis of the errors when only the ellipsoid was visible in an otherwise completely dark room suggests that the distance used for scaling retinal disparity is indeed the same as that used for scaling retinal size. This was confirmed by showing that the correspondence between the distance used for scaling retinal disparity and that used for scaling retinal size does not improve when more information about distance is available (room lights on), although both distances are then much closer to the simulated distance. Finally, we show that this correspondence is not due to the use of distance-invariant higher order binocular information.
Charging for health services in developing countries.
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Hepaticoportal fistula and portal hypertension.
A large intrahepatic fistula between the hepatic artery and portal vein was detected at angiography in a patient with portal hypertension and bleeding esophageal varices. Hemodynamic studies demonstrated that increased vascular resistance in the liver rather than increased flow through the fistula was responsible for the portal hypertension and a portocaval shunt was performed. A repeat angiogram two months after the operation showed that the fistula had closed spontaneously.
Automated assay of gamma-aminobutyric acid in human cerebrospinal fluid.
We describe an automated amino acid analyzer with fluorescence detection (o-phthalaldehyde) which permits sensitive and rapid determinations of gamma aminobutyric acid in human cerebrospinal fluid. Concentrations as low as 50 nmol/liter can be accurately determined in 100 mul samples at the rate of one sample per hour. Concentrations in untreated cerebrospinal fluid increase rapidly after sampling by lumbar puncture. The concentration in immediately deproteinized samples from 38 patients with intervertebral disc disorders was 220 +/- 81 nmol/liter (mean +/- SD).
A radiological study of the effects of smoking on regional differences in the lung.
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Arterial and venous signs of tumors within the fourth ventricle.
A positive diagnosis of tumors located within the fourth ventricle should be based on specific signs therby excluding other space occupying lesions in the posterior fossa. These are a typical omega form of the hemispheric cerebellar branches on the lateral projection, and an also typical inverted 3 form of the PICA in the semiaxial projection. Alteration of the veins of the lateral recess of the fourth ventricle and of the precentral cerebellar vein are important venous signs. Indirect signs are found in the absence of tonsillar herniation with arterial and venous signs of AP stretching of the cerebellar tonsils.
Computed tomography in ophthalmology. Density changes with orbital lesions.
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A standardized method for computed tomography of the orbits.
A standardized method for the CT exploration of the orbital region has been searched for. This method makes it possible to visualize the entire orbital region with a minimum of 4 tomographic scans, each section 6 mm thick. The reference line chosen for this exploration is parallel to the optic nerve and joins the projection of the inferior border of the orbit on the lateral view with the upper border of the ear to the scalp. After each tomographic scan the patient is moved so that the new scanning line is still parallel to the reference line but distant by 9 mm from the previous one.
A new method of localize the choroid point of the PICA and the venous copular point on the lateral projection of vertebral angiography.
The location of the choroid arterial point as well as of the copular venous point with reference to a line, dealing with the anatomical structure at the level of the cervicooccipital joint, was found to be a quick and accurate method for the diagnosis of tonsillar herniation. The application of this method has the advantage of giving the location of the choroid arterial point, and a control of the venous time of arteriography by the location of the copular point.
Tolosa-Hunt syndrome, phlebographically controled after recovery.
A 27 year old patient, presenting clinically and phlebographically a Tolosa-Hunt syndrome was observed after recovery. Normal reappearance of a previously completely obstructed cavernous sinus was noted, leaving only a persisting irregularity of the superior ophthalmic vein.
Renal rumour with minor adenocarcinomatous and major osteosarcomatous components.
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