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Biomedical subjects

W Döhring

Publications and source records attributed to W Döhring.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1984

[Computed tomography of malignant stomach tumors].

Forty-four patients with malignant disease of the stomach (41 carcinomas, three non-Hodgkin lymphomas) and two patients with chronic gastric ulcers were examined by computer tomography before undergoing surgery. The ulcers, the non-Hodgkin lymphoma and the carcinomas stages pT2 to pT4 were easily demonstrated, as well as 66% of carcinomas in stage pT1. In addition to the primary tumour, it was possible to recognise lymph node and organ metastases. Two of the 46 patients were not submitted for surgery because of extensive metastases.

Adult↗
PubMed1983

Value and limitations of computed tomography in assessing aortocoronary bypass graft patency.

To determine the value of nondynamic computed tomography (CT) in assessing aortocoronary bypass graft patency, we studied 67 patients with 125 grafts by CT and by coronary angiography at close time intervals. CT scans were performed before and after one to three (average 1.98 +/- 0.65) 50-ml i.v. bolus injections of contrast material. Eighty-four of 92 grafts patent at angiography were also visualized by CT (sensitivity 91.3%); 29 of 33 grafts closed at angiography were considered to be occluded by CT (specificity 87.9%). Eleven of 13 grafts demonstrating one or more severe obstructions at angiography were considered to be patent by CT. Interobserver disagreement existed in four of 125 grafts (3.2%) and intraobserver variability was 1.6%. Although nondynamic CT allows a correct assessment of graft patency in many cases, it does not provide sufficient information on graft stenosis and function to replace angiography in patients who are symptomatic after surgery.

Adult↗
PubMed1982

[Indication and efficiency of computer tomography in heart and thorax surgery].

Computed tomography has widened the diagnostic and indicatory potential in thoracic and cardiovascular surgery. The method allows discovery and localization of discrete pathological findings thus far evading routine diagnostics. Under certain conditions tissue may be characterized and a tumor staging performed. Computed tomography cannot replace preoperative angiography but is useful for noninvasive postoperative screening. The value of the procedure in diseases of the lung and pleura, the mediastinum, and the cardiovascular system is demonstrated.

Bronchial Neoplasms↗
PubMed1982

[Focal nodular hyperplasia of the liver--is a radiologic diagnosis possible? (author's transl)].

Focal nodular hyperplasia of the liver (FNH) is a histologically defined benign tumor, which can be distinguished from other space-occupying diseases of the liver. The present paper deals with the question whether FNH can be distinguished from other lesions of the liver by a combination of radiologic procedures. Therefore 10 patients with FNH of the liver underwent sonography, hepatic scintigraphy, computed tomography with dynamic CT--densitometry, and angiography. The computed tomography with dynamic CT--densitometry using intravenous bolus injection of contrast medium seems to be the most accurate method for detection of FNH of the liver.

Adolescent↗
PubMed1981

[Angiographic and CT diagnosis of aortic aneurysms (author's transl)].

18 patients with aortic aneurysm were examined by angiography and computed tomography. Dissection was found in 10 Patients. It was not possible to accurately determine the proximal and distal extension of the aneurysms via any of the two methods. Vascular sclerosis and thrombi were more clearly visualised in the computer tomogram, but it was not always possible to accurately visualise vascular ramifications. In spite of the fact that the informative value of the computer tomogram is not always satisfactory if effected preoperatively, especially with dissecting aneurysms, a CT should be done as far as possible before angiography.

Adult↗
PubMed1981

[Modified CT imaging by reduction factor transformations (author's transl)].

The possibilities of CT image modification which had existed so far for given matrix of attenuation values (window setting, highlighting, black-and-white or colour reversal and logarithmic distortion of the video signal) are supplemented by the method of attenuation value transformation. As a specific case a linear interval by interval attenuation value transformation is described. First of all, the intirety of the measured CT values is transformed into the corresponding CT quotients (CTQ) and then subdivided into 5 optional intervals. Each one freely selected CTQ value can be allocated to the first and to the last interval; the intermediate 3 intervals can be linearly transformed at random. The article discusses the influence of such a manipulation on CT image reproduction; this is of particular importance for the image visualisation of the results of quantitative organ analyses by means of computed tomography. The presented paper also points to the possibility of effecting further attenuation transformations.

Brain Neoplasms↗