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Biomedical subjects

W Döhring

Publications and source records attributed to W Döhring.

At least 19 recordsLinked to original sources
PubMed1992

[Arthritic changes in small and large joints in digital and conventional x-ray images].

In order to evaluate the suitability of digital radiography for the diagnosis of skeletal abnormalities, inflammatory joint changes were used to test this technique. Early erosive changes, fine irregularities and marginal lamellar abnormalities demand a high degree of resolution from the imaging method. 6 observers studied images of the hand of 67 and of the foot of 19 patients. Joint changes were staged according to the scheme proposed by Larsen; in this study the early stages predominated. With similar techniques there were no significant differences between the digital and conventional techniques. Images of 39 large joints (knee, shoulder, elbow, ankle) were compared only subjectively since even minor differences in projection were able to obscure some erosions. However, in this case also both techniques appear to be of similar value.

Adult↗
PubMed1991

[Digital luminescence radiography . 2: Technical implementation and clinical application--future developments].

In the previously published Part 1 of this paper the basic principle of digital luminescence radiography (DLR) was presented and the technical implementation of the data acquisition system with its advantages and disadvantages as compared with conventional radiography were described [3]. Part 2 covers processing, display, archiving and communication of image data; in addition, suggestions for future improvements in the technique are made. Image processing research is directed towards optimal presentation of the detected data by spatial frequency filtering with unsharp masking and by gradation enhancement. Additional information can be acquired by means of dual energy investigations. The image is displayed on either monitor or transparent X-ray film. Picture archiving requires large storage capacities, and picture communication needs fast transfer rates. At present, about 450 installations for digital luminescence radiography are in clinical use worldwide. Routine use can be expected when technical improvements have been implemented.

Humans↗
PubMed1991

[Digital luminescence radiography. Part 1: Basic principle, technical execution and clinical use].

Digital luminescence radiography (DLR) is a new technique in projection radiography, which enables the production of plain X-ray images and motion tomographies with high quality, and is suitable for digital image management. With this procedure the X-ray image produced by conventional roentgen devices is temporarily stored on a reusable photostimulable storage phosphor screen which is characterized by a wide dynamic range. A laser beam scans the exposed phosphor screen and recovers the stored X-ray information as photostimulated luminescence radiation. A photomultiplier converts the emitted light into electrical signals. After normalization and digitization the signals are transmitted to an image processor. The stored digital image can be individually processed and displayed, digitally archived or transferred to any location. The technique is described in two following papers. Part 1 covers the basic principle of the system and the technical implementation of the data acquisition with its advantages and disadvantages as compared with conventional film/screen radiography.

Equipment Design↗
PubMed1990

[Chemical embolization of carcinoid metastases in the liver].

We performed chemo-embolisation with gel foam powder and epirubicin in 11 symptomatic patients with liver metastases from carcinoids. In all cases the symptoms regressed completely after the procedure. In two patients the liver was re-embolised because of tumour growth and both again became symptom-free. In one case, increasing extra-hepatic tumour growth was treated with interferon. One female patients died seven days after the procedure from renal failure and from complications of cerebral oedema. Two other patients died from extensive extra-hepatic tumour in the skeleton and lungs at 88 and 97 weeks after embolisation, respectively. The remaining patients are still symptom-free at 18 to 161 weeks.

Adult↗
PubMed1989

[Computed tomographic detection of chemotherapy-induced thymus changes in patients with metastatic testicular tumors].

Serial thoracic CT scans of 100 patients suffering from testicular cancer revealed that the thymus appears to atrophy temporarily during administration of cytostatic agents. About two months after cessation of chemotherapy rebound enlargement of the thymus occurs and persists for about two years followed by a slow involution. Using a semiquantitative score system, thymic CT images of these patients were compared with that of 100 patients suffering from other malignancies, 100 patients without malignant disease and 52 patients with myasthenia gravis, taking into account the age-related changes of the size of the organ. Rebound thymic enlargement should not be misinterpreted as metastatic lymph nodes.

Adolescent↗
PubMed1986

[Program system for quantitative evaluation of computed tomograms using a digital masking technic for isolation of organs of interest and organ regions from the value matrix].

A program system for the quantitative analysis of CT images is described and its versatile applicability is demonstrated by practical examples. Using a semi-automatic digital masking technique, the system allows to isolate single organs or regions of organs with good reproducibility and to process their CT values separately. For processing of the complete image matrix or of isolated areas of the matrix, evaluation programs have been developed, which--in addition to the standard image evaluation functions available in modern CT systems--provide the possibility for various CT value transformations and special statistical analyses of original and transformed CT values. The demonstrated applications of the program system include determination of the venous capacity of the lower extremities by CT, separation of different components of the brain from a cranial CT, ventilation analyses of the respiratory lung parenchyma, calculation of the fat content in a fatty liver and approximate measurement of the iodine concentration in a contrast-enhanced kidney.

Brain↗
PubMed1986

[Computed tomographic and sonographic detection of renal and perirenal changes following shockwave lithotripsy].

The finding of a major haemorrhage after lithotripsy induced us to look at 42 patients undergoing extracorporeal lithotripsy by CT and by sonography, both before and after the procedure, in order to determine the frequency of bleeding. In 37 patients, significant bleeding was found in the perirenal tract and in Gerota's capsule. There were six small sub-capsular haematomas which were not found by sonography and two extensive renal haematomas.

Adult↗
PubMed1985

A simple device for breath-level monitoring during CT.

Computed tomography (CT) of the chest and abdomen requires well-defined and reproducible breath-holdings. For this purpose, a simple respiration-control device has been developed that enables the patient to monitor breath-holding during successive scans. The patient holds his/her breath at a preselected level using feedback monitoring. The device is easy to handle and suitable for all commercial CT systems.

Humans↗
PubMed1978

[Polarographic measurements of PO2 with a 95% response time of 7-10 msec (author's transl)].

A fast PO2 tracing with 95% delay times of 15-20 msec in routine is necessary for measurement of the PO2 jumps in the expired air, particularly for the precise measurement of the so-called dead-air plateau. A Clark type PO2 electrode has been developed which has the demanded property. This electrode has four characteristic features: (1) a glasscoated Pt cathode with a tip diameter of 0.3 mm (diameter of the Pt wire = 0.1 mm); (2) a differential screwdrive for feeding the cathode 50 micrometer per turn; (3) a 0.2- to 0.3-micrometer-thin polytetrafluorethylene membrane, and (4) a special polishment of the surface of the cathode. The electrode has a 95% response time of 15-20 msec in routine when tracing PO2 changes from 150 to 750 mm Hg. About 30% of the prepared electrodes have response times of 7-10 msec. The output of the electrode in air is stable within the first 3 h (deviation smaller than 0.2%) and then decreases within 10 h approximately 1% per hour. The response times are constant for more than 48 h. The output of the electrode is linear from 0 to 760 mm Hg PO2. Within the accuracy of measurement the output is independent of PCO2.

Electrodes↗
PubMed1978

[An improved modification of the micro-method according to Niesel and Thews for the measurement of O2-hb binding curves in whole blood and concentrated Hb solutions (author's transl)].

An improved modification of the photometric micro-method according to Niesel and Thews is described, which employs the diffusion principle. The O2-Hb binding curves of whole blood or concentrated Hb solutions (0.1-30 g%) can be measured within 0.5 h. Sample volume is approximately 7 microliter, wavelength is 578 nm. Several reproductions of the curve may be measured with one sample. The reproducibility of P50 is 0.5 Torr. In comparison with the Van Slyke method no systematic error is found.

Hemoglobins↗