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Biomedical subjects

N G Holmer

Publications and source records attributed to N G Holmer.

At least 19 recordsLinked to original sources
PubMed1992

Demonstration of digital radiographs by means of ink jet-printed paper copies: pilot study.

Different digital medical images have been printed on paper with a continuous ink jet printer, and the quality has been evaluated. The emphasis has been on digital chest radiographs from a computed radiography system. The ink jet printing technique is described as well as the handling of the image data from image source to printer. Different versions of paper prints and viewing conditions were compared to find the optimum alternative. The evaluation has been performed to maximize the quality of the paper images to make them conform with the corresponding film prints and monitor images as much as possible. The continuous ink jet technique offers high-quality prints on paper at a considerably lower cost per copy compared with the cost of a film print. With a future switch-over from diagnosing of digital images on film to diagnosing them on monitors, hard copies for demonstration purposes will occasionally be needed. This need can be filled by ink jet-printed paper copies.

Copying Processes↗
PubMed1991

On the mechanism of kidney stone disintegration by acoustic shock waves.

In the present study we have, by theoretical and experimental investigations, especially concentrated on the importance of acoustic streaming, transient cavitation and microstreaming in the fluid close to the stone. Artificial stones, round stones 20 mm in diameter made of Plaster of Paris or rectangular flat stones, 25 x 25 x 15 mm, were suspended in a water bath at the focus of an EDAP LT01 lithotripter. "Unprotected" stones were disintegrated while stones surrounded by a layer of silicone showed no or very small disintegration. For successful destruction of the calculus, it seems to be essential that the stones are surrounded by a liquid, i.e., water.

Humans↗
PubMed1991

Analysis and classification of secondary sounds from the disintegration of kidney stones with acoustic shock waves.

Secondary sound emission, partly in the audible frequency range, from shock wave disintegration of kidney stones has been recorded during the treatment of two patients. A skilled operator can determine by listening if the stone is hit by the shock-wave or not. Spectral analysis of these recordings show differences between the sounds which can be used to evaluate the fragmenting effect on the stone. Results are presented of a preliminary discriminating method based on parameters in an autoregressive signal model.

Humans↗
PubMed1991

A measurement system for continuous wave ultrasound fields.

A measurement system for evaluating ultrasound fields is presented. The system utilizes a PVDF hydrophone and a mechanical scanning device. For continuous wave (CW) ultrasound, a high sensitivity is achieved by using a narrow band technique. The high sensitivity is demonstrated in a recording of the beam profile from an air transducer. Recordings from fetal Doppler equipment shows that, due to interference between the multiple transmitters, a high spatial resolution is needed in the field measurements in order to obtain correct values for peak intensities.

Female↗
PubMed1991

Registration of surface structures using airborne focused ultrasound.

A low-cost measuring system, based on a personal computer combined with standard equipment for complex measurements and signal processing, has been assembled. Such a system increases the possibilities for small hospitals and clinics to finance advanced measuring equipment. A description of equipment developed for airborne ultrasound together with a personal computer-based system for fast data acquisition and processing is given. Two air-adapted ultrasound transducers with high lateral resolution have been developed. Furthermore, a few results for fast and accurate estimation of signal arrival time are presented. The theoretical estimation models developed are applied to skin surface profile registrations.

Humans↗
PubMed1991

The use of ink jets in ultrasound registrations.

The continuous ink jet method developed by Professor Hellmuth Hertz, Lund Institute of Technology, Sweden, is today used in printers that print digitally stored high-quality images rapidly and at low cost. The development started in the late 1950s when there was a need for a direct registration method for ultrasound echocardiograms. The development steps are described from the early ultrasound registrations to the true halftone printing of digital images today. Images from ultrasonic color Doppler examinations have been printed by an ink jet printer at our laboratory. The color capabilities of the printer are further illustrated by the printing of pseudo-colored gray-scale images and an image where color is used to highlight differences between two gray-scale images. The results show that the printer based on continuous ink jets is an interesting alternative to the existing hard-copy devices for medical images.

Echocardiography, Doppler↗
PubMed1983

The pulsed ultrasound method adapted for examination of paranasal sinuses.

Three different ultrasonic display systems for examination of paranasal sinuses (oscilloscope; light emitting diodes; gas discharge display) have been evaluated in model experiments, on healthy subjects and in clinical materials. With the three different ultrasonic display systems air could be separated from other types of sinusal contents in model experiments. The detectable amount of saline solution in normal sinuses was 1-5 ml with all display units. The different display units showed the same screening capacity as radiography. The oscilloscope display system was significantly more efficient than the other display systems in separating different pathological conditions. Also regarding radiography the oscilloscope display was significantly more efficient in detecting secretion, but no difference was found in the capacity of predicting intrasinusal cysts. Thus, the oscilloscope display seems to be the most useful for both clinical and scientific purposes.

Humans↗
PubMed1982

The effect of transistor-regulated direct current on non-fractured rabbit femur.

An experienced study was performed to examine the effects of transistor-regulated 20 microampère direct current on rabbit femur and to evaluate methods of measuring the effects. The anode and the cathode were both placed in drill holes in the anterior aspect of the cortex of the right femur, the left femur being used as a control with the electrodes without current. The effects of the electrical stimulation were evaluated by means of roentgenograms, photomorphometric measurements of the cortical width and measurements of bone volume, ash-weight and 85Sr uptake. In the roentgenograms it could be seen that osteogenesis was induced both at the anode and the cathode. Also, an increased uptake of 85Sr was demonstrated indicating an increased bone formation rate.

Animals↗
PubMed1982

Electrical stimulation of osteogenesis: studies of the cathode effect on rabbit femur.

Three series of experiments were performed to evaluate the effect of 20 microampère constant direct current on rabbit femora. Stainless steel cathodes were introduced into the medullary cavity and anodes were placed subcutaneously. Both femora were operated on in the same manner but only the right femur was stimulated electrically. The osteogenic effect was determined histomorphometrically in two of the series. No difference in osteogenic response between the right and the left femora was found. In the third series, the femora were divided into proportionally equal parts and bone volume, ash-weight and activity of 85Sr were determined. A non-significant increase in new bone formation in the cathodal region of the right femora was noted. Our conclusion is that direct cathodal current has a weak stimulating effect on new bone formation in rabbit femora.

Animals↗