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Biomedical subjects

W Dölken

Publications and source records attributed to W Dölken.

At least 19 recordsLinked to original sources
PubMed2006

Technical note: gold marker implants and high-frequency jet ventilation for stereotactic, single-dose irradiation of liver tumors.

With reference to radiosurgery of the liver, we describe techniques designed to solve the methodological problem of striking targets subject to respiratory motion with the necessary precision. Implanting a gold marker in the vicinity of the liver tumor was the first step in ensuring the reproducibility of the isocenter's position. An 18-karat gold rod measuring 1.9 x 3 mm was implanted approximately 2 cm from the edge of the tumor as this was displayed in the spiral, thin-slice CT with contrast media. Both the implantation of the marker and the required, CT-controlled biopsy of the liver tumor can be achieved simultaneously with the same puncture needle. The efficiency of high-frequency jet ventilation (HFJV) in neutralizing the targeted organ's respiratory motion during stereotactic single-dose irradiation was evaluated. The procedure was carried out on ten patients without any complications. In the time between treatment planning and irradiation (3 days), no significant marker migration was observable. In all cases, the gold marker (volume: 7.5 mm(3)) was readily observable in the treatment beam using portal imaging. HFJV provided reliable immobilization. The liver motion in each anesthetized patient was limited to under 3.0 mm in all directions. Thus, the correct field settings and target reproducibility were able to be analyzed and documented during the irradiation. The combination of marker and HFJV enables the determination of stereotactic coordinates directly related to the liver itself and, in this way, stereotactic radiation treatment of liver tumors is freed from the uncertainties involved in orientation to bony landmarks, in respiratory motion, and in changes of position in the stereotactic body frame. The method is feasible and can improve the accuracy of stereotactic body radiation therapy.

Gold↗
PubMed1998

[Digital selenium radiography: a comparison of the picture quality of thoracic images in normal and reduced image formats based on the structural anatomical details].

PURPOSE: Is there a loss of information when using selenium radiographic images displayed with reduced image format compared to full format? METHOD: Digital selenium radiographic chest images in two planes were obtained in 35 patients for medical reasons. The digital data sets of each patient were separately displayed in full format on two different films and were printed in reduced format on one film. The format was reduced to 61% of the full format using an acquisition matrix of 2166 x 2488 pixels, an image display matrix of 4000 x 5000 pixels and a film format of 43 x 49 cm. All images were anonymously evaluated by four independent readers using a questionnaire concerning anatomic structures. RESULTS: Format reduction did not result in a loss of information in diagnostically relevant anatomic details. CONCLUSIONS: Displaying digital selenium radiographic data sets of thoracic view in two planes on one film presumably does not lead to a loss of diagnostic information. This procedure may help to reduce film costs.

Adult↗
PubMed1997

[Cystic form of Pneumocystis carinii pneumonia].

BASIC PROBLEM AND OBJECTIVE: In rare instances Pneumocystis carinii pneumonia (PCP) can occur in a cystic form, characterized by an acute course. The correct diagnosis is often missed. An analysis of a large cohort of patients with PCP was undertaken to determine the incidence and clinical manifestations of this form of the disease. PATIENTS AND METHODS: Data on all HIV-positive patients on the hospital registry, hospitalized with the diagnosis of PCP between January 1988 and July 1996, were retrospectively analysed. To be included in the study, PCP had to have been confirmed microscopically on bronchial lavage or histologically by lung biopsy. The chest radiogram and (if available) computed tomogram of these patients were examined for possible cystic changes, and clinical as well as laboratory findings recorded. RESULTS: Five of 180 patients with PCP had cystic changes (2.8%). The interval between first symptoms and diagnosis ranged from 30 to 200 days (median: 32 days). All five patients (age: 24-49 years; all males) had a far advanced immunological disorder (median CD4 count: 10/microliter) and were in stage C3 (Centers for Disease Control). Three of the five patients had prophylactically inhaled pentamidine (300 mg/month). Bronchial lavage was false-negative in three of the five cases. One patient had a spontaneous pneumothorax. Lactate dehydrogenase levels were normal or only slightly elevated (207-417 U/l; median 305 U/l). Both the cavities and thin-walled cysts were demonstrated radiologically, but were more visible on CT than on the X-ray film. All patients responded well to the medication with cotrimoxazole, but the prognosis was poor with a survival time of only 0.3 to 16 months. CONCLUSION: PCP should be included in the differential diagnosis when HIV patients have cystic lung changes. Invasive diagnostic methods are often required to avoid wrong diagnosis and superfluous therapeutic interventions.

Adult↗
PubMed1997

[Can digital selenium-based radiography in thoracic diagnosis replace the analog x-ray imaging technic?].

PURPOSE: To find out the diagnostic value of digital selenium radiography, we compared the image quality of chest x-ray images from 50 patients who had been examined via conventional chest x-ray and digital selenium radiography of the chest. METHOD: 50 patients with a malignant melanoma underwent chest x-ray within 3 months in conventional technique and with digital selenium radiography (Thoravision: Philips Medical Systems, Hamburg, Germany). In this period none of the patients showed a difference in respect of clinical status or radiological diagnosis. Simultaneous examinations on the same day were not performed to avoid unnecessary exposure to x-rays. The digital and conventional images were compared by 4 radiologists with regard to image quality by the detection of defined anatomic structures. RESULTS: Image quality of digital selenium radiography was considered superior to that of conventional chest x-rays in the mediastinum, the retrocardiac and retrodiaphragmatic areas, the superior and inferior lobes of the lung especially near the parietal pleura, and the chest wall. CONCLUSIONS: Compared to analogous techniques there is no loss of image information when employing digital selenium radiography in chest x-rays. On the contrary, new assessment criteria may be gained. We conclude that digital selenium radiography offers diagnostic advantages in chest x-ray examination.

Adult↗
PubMed1996

Angiographic detection of gastrointestinal bleeding. An experimental comparison of conventional screen-film angiography and digital subtraction angiography.

RATIONALE AND OBJECTIVES: The authors experimentally assess and compare the detection limit of gastrointestinal bleeding in digital subtraction angiography (DSA) and conventional screen-film angiography. MATERIALS AND METHODS: Arterial blood flow was simulated using a tube model in which bleeding was imitated by exudation of liquid containing contrast material. Gut peristalsis was imitated using silicone tubes filled with air and liquid. Images were acquired by DSA and conventional screen-film angiography. The iodine concentration was increased in increments from 1 mg I/mL, with and without simulated peristalsis, and with both free and circumscribed extravasation of contrast material. RESULTS: The detection limit for free extravasation in DSA was 1 mg I/mL without peristalsis and 60 mg I/mL with peristalsis. The corresponding figures for circumscribed extravasation were 1 mg I/mL and 34 mg I/mL. The detection limit for free extravasation in screen-film angiography was 172 mg I/mL both with and without simulated peristalsis. Circumscribed extravasation was detected at 9 mg I/mL without peristalsis and 7 mg I/mL with peristalsis. CONCLUSION: Digital subtraction angiography is the more sensitive angiographic technique for detection of gastrointestinal bleeding and is superior to conventional screen-film angiography, provided that it is performed with adequate parasym-pathicolysis and suspended respiration. Only when these requirements cannot be achieved is screen-film angiography advantageous.

Angiography↗
PubMed1994

[Congenital duodenal obstruction in combination with heterotopic gastric mucosa in the gallbladder. Case report and etiology].

A hitherto unique case of ectopic gastric mucosa of the gallbladder in combination with a congenital duodenal stenosis in an young male adult is presented and the etiology of both anomalies is elucidated. While the intestinal obstruction was confirmed prior to the operation, the diagnosis of the gastric heterotopia in the gallbladder has been established, as usually, first by histopathologic examination. Both anomalies required surgical treatment. The long-standing indistinct abdominal complaints of the patient vanished after cholecystectomy and duodenojejunostomy.

Adult↗
PubMed1993

[X-ray studies of the peripheral joints: a comparison of digital luminescence radiography (DLR) and film-screen systems].

175 matched skeletal x-ray examinations were carried out by digital luminescent radiography (DLR) and conventional screen-film system combinations. In digital luminescent radiography (DLR) two differently postprocessed images were obtained from one x-ray exposure: A display with low spatial frequency enhancement was opposed to a second display with high edge enhancement. Conventional and digital images were evaluated randomly and separately by four radiologists using a questionnaire. DLR proved to be diagnostically equivalent to the conventional technique except for a diminished visibility of subtle erosions and fissures. As major advantages of DLR maybe pointed out that faulty exposures were avoided by the automatic adjustment of image brightness and that the soft tissue margins could be more easily delineated in displays with high edge enhancement than in conventional radiography. However, digital displays with high edge enhancement did not provide additional diagnostic information and led to artifacts at the edges of metal prostheses.

Adult↗
PubMed1992

[Interstitial lung diseases. A comparative study between a film-screen combination and a digital storage phosphor technic].

Chest examinations were carried out in 60 individuals using film-screen and digital storage phosphor techniques and identical radiation doses. 29 of these individuals were patients with interstitial pulmonary disease; 31 were normals. Postprocessing of the digital images was carried out with filtering using an unsharp mask and identical parameters for all patients. An ROC analysis using 10 observers showed no significant difference in the evaluation of the interstitial lung disease. Correlation analysis showed a significant positive correlation (p less than 0.001) for the findings in both techniques. Under the present circumstances, film-screen and digital storage phosphor technique are of equal value in the diagnosis of interstitial pulmonary disease.

Adult↗
PubMed1992

Spontaneous thrombosis of the renal vessels. Rare entities to be considered in differential diagnosis of patients presenting with lumbar flank pain and hematuria.

We report 2 cases of spontaneous thrombotic occlusion of the main renal vessels presenting with acute lumbar flank pain and hematuria suspect of nephrolithiasis. Clinical and laboratory signs of blood hypercoagulability, generalized arterial embolism, nephrotic syndrome or glomerulonephritis were absent. Excretory urography, nephrosonography and retrograde ureteropyelography showed no evidence of upper urinary tract calculi or other causes of obstruction. Renal angiography and cavography demonstrated an acute renal vein thrombosis in 1 patient and a thrombotic occlusion of all but one of the segmental renal arteries in the other patient. These 2 cases demonstrate that thrombotic occlusion of the renal artery or renal vein has to be considered in patients who are presenting with lumbar flank pain and hematuria, in whom the excretory urogram shows severe malfunction of one of the kidneys, and stone disease can be excluded. Renal angiography and cavography as well as CT scan should be carried out in these patients. When the disease is diagnosed at an early stage, an intra-arterial thrombolysis can be attempted.

Acute Disease↗
PubMed1991

Quantification of vascular stenosis with color Doppler flow imaging: in vitro investigations.

The accuracy of quantifying the degree of vascular stenosis with color Doppler flow imaging (7.5-MHz, linear array system) was determined in an experimental study carried out on six concentric and five eccentric model stenoses (cross-sectional area reduction, 13.4%-93.8%). The measurements were made with use of pulsatile flow at four different flow rates (70.8-339.0 mL/min). The degree of stenosis was calculated from the ratio of prestenotic to intrastenotic flow velocity. The most exact measurement of the degree of stenosis could be achieved with Doppler spectral analysis by determining the maximum peak systolic velocity (r = .994, y = 0.98x - 3.2). With the velocity values derived only from the color-coded image, it was also possible to find the most exact degree of stenosis (r = .995, y = 0.99x - 2.9). For quantification of stenosis, pre- and intrastenotic Doppler spectral analysis is no longer necessary if the stenosis can be imaged sufficiently with color Doppler.

Blood Flow Velocity↗
PubMed1991

[A ROC analysis for comparing contrast perception in grey scale reversal of digital images].

Based on ROC (receiver operating characteristic) analysis, contrast perception by eight physicians engaged in x-ray diagnostics for different lengths of time was examined in respect of inversion of grey scale values of digital x-ray film images. The ROC analysis showed a significantly superior contrast perception for imaging by the negative mode (bones white) than by the positive mode (bones black). With r* = + 0.61 a positive correlation was obtained between the period of the physicians' activity in x-ray diagnostics and the difference between the areas below the ROC curves for both imaging modes. Hence, the negative mode is to be preferred for diagnostic work based on digital x-ray film images.

Humans↗
PubMed1990

[Gadolinium-DTPA as an oral contrast medium for MR tomography of the abdomen].

150 MR examinations of the upper abdomen were carried out after the oral administration of 5 ml/kg body weight of a gadolinium DTPA formulation (1.0 mmol/l, 15 g/l mannitol), with reference to the delineation of the pancrease, the liver and intra-abdominal fat. For comparison, 100 MR examinations without oral opacification of the G.I. tract were evaluated. Contrast administration resulted in a signal-intensive demonstration of the G.I. tract for all measurement sequences. The intraluminal contrast improved the distinction between normal and abnormal structures. T1 and T2 sequences and the demonstration of fat on T2-weighted series. T1-weighted series showed the best diagnostic results. In 25% there was meteorism and diarrhoea within 24 hours of the administration of the oral contrast.

Abdomen↗
PubMed1989

[Imaging properties of digital image-intensifier radiography compared to the conventional x-ray technic for chest pictures].

Projection properties of a digital fluorographic system for chest examinations are examined using varying test phantoms. A maximal geometric distortion of +14% between the centre and the periphery of the image intensifier and a maximal spatial resolution of 2.6 LP/mm is found. Contrast detail diagrams are used to show the combination of spatial and contrast resolution of the system. Compared with diagrams for conventional radiographic systems there is a significant loss of resolution.

Adolescent↗
PubMed1989

[In vitro measurement of intravascular blood flow with color Doppler sonography].

The accuracy of colour Doppler sonography for measuring various aspects of intravascular flow (volume and velocity), under varying conditions, was studied experimentally. The effect of variable Doppler angles, different flow paths, frequency and vessel diameter on flow profiles was examined. At all levels of measurement (range 14 ml/min to 566 ml/min) there was a very close correlation between the actual and measured values (r greater than 0.99) and high accuracy. In the detection of very slow flow rates, the use of a specific high pass filter technique was able to quantify blood flow velocities of just under 1 cm./second. Multigated colour Doppler sonography is better for measuring flow volumes than a single channel duplex system.

Blood Flow Velocity↗
PubMed1989

[High-resolution MR tomography of the hand: normal anatomy].

By using surface coils and a high resolution matrix, the images from MR tomography of small objects can be greatly improved. Normal subjects have been examined in order to demonstrate the usefulness of MR tomography for the examination of bones and soft tissues in the normal hand.

Adolescent↗