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Biomedical subjects

M Georgi

Publications and source records attributed to M Georgi.

At least 19 recordsLinked to original sources
PubMed1992

[MR angiography of the vertebrobasilar circulatory area: the potential uses of the saturation technic to determine the direction of the flow].

MR angiography (MRA) combined with selective saturation techniques has proved to be a reliable method for the determination of flow direction and vascular supply at the level of the circle of Willis. We describe its application to the vertebrobasilar system (VBS) in ten volunteers and five patients with abnormal findings. In one patient with postsurgical stenosis of the brachiocephalic artery, reverse flow of the vertebral artery (VA) was demonstrated. Collateral blood flow from the anterior circulation over the posterior communicating arteries was shown in three patients with bilateral vertebral or proximal basilar artery occlusion. Due to increase of pressure during contrast injection into the contralateral VA, DSA showed reverse flow of a dissected VA in one patient. MR flow determination as well as TCD proved antegrade flow. All results correlated with both DSA and transcranial Doppler (TCD). The technique is little time consuming and is a promising add-on examination to conventional and MRA imaging of the VBS.

Adult↗
PubMed1992

[MR tomographic studies of the cerebral circulation: the methodological principles and initial clinical experiences with T2*-weighted gradient-echo sequences and CM administration as a bolus].

Paramagnetic contrast agents produce local magnetic field inhomogeneity when they pass through the cerebrovascular system. This effect can be monitored with T2*-weighted gradient echo images, which show transient signal loss, while a bolus of GdDTPA is passing through the brain tissue. This signal loss is correlated to the local cerebral tissue perfusion and the local cerebral blood volume. In a prospective study 10 volunteers and 14 patients with cerebral infarcts and brain tumours were examined. After bolus application of GdDTPA a dynamic series of rapid T2*-weighted gradient echo images were recorded, and the local dynamics of contrast flow in brain tissue was examined. From the series of images, local changes in signal intensity were calculated pixel by pixel and presented as parameter images. By this method, infarcted areas and brain tumours can be distinguished from normal tissue by their contrast flow dynamics. The abnormal contrast dynamics depend on changes in local tissue perfusion and alterations in local blood volume. The separation of the influence of both parameters however is still an unsolved problem.

Adolescent↗
PubMed1992

[Thoracic radiographs with the AMBER system. A comparison of the diagnostic image quality of film-screen and storage-phosphor radiographs on the grid-partition stand and the AMBER system].

Since April 1990, chest radiographs in the Mannheim clinic have been performed with a slit technique (Kodak AMBER System). In this study, image quality from conventional film/screen combination and from storage phosphor radiography was compared with that from the AMBER system. Phantoms were used to measure spatial resolution and to determine the detectability of nodules. Image quality affecting various structures within the thorax was evaluated on 200 p.a. and 48 lateral radiographs by three radiologists from Mannheim and four from Berlin. In the retrocardiac, retrodiaphragmatic, mediastinal and peripheral portions the best image quality was obtained by film/screen with the AMBER system. Compared with conventional film/screen images, there was no improvement from the AMBER system within the lung parenchyma. The use of storage phosphor plates with the AMBER system did not lead to any further improvement in image quality.

Evaluation Studies as Topic↗
PubMed1992

[Do the obstetrically relevant bony pelvic measurements change? A retrospective analysis of computed tomographic pelvic x-rays].

The important dimensions of pelvimetry were evaluated from 467 CT studies of the pelvis by trigonometric deduction. The age of the women was between 18 and 88 years. In addition to the diameters, which are routinely used for pelvimetry, transverse and sagittal diameters, pelvic angles and areas of pelvic planes were calculated. On condition that the pelvic dimensions do not depend on age the parameters can be regarded as representative of sexual maturity. 5 parameters showed highly significant and 7 parameters showed significant differences between the age-classes 1901-1920 and 1950-1971. An increase of pelvic dimensions (1950-1971) was found at the planes of the pelvic inlet and outlet in contrast to the dimensions of the pelvic center. The results confirm the importance of the bispinous diameter for pelvimetry as well as the demand for a revision of the standard values of the first half of the century.

Adolescent↗
PubMed1992

[Magnetic resonance tomography as the basis for biomechanical analysis. The simulation of the birth process as an example of the expanded information potentials of segmental imaging procedures].

A method is presented that enables the use of (static) informations from magnetic resonance imaging (MRI) for (dynamic) biomechanical analysis. Using a specially developed software MRI pixel matrices are colour-coded and--according to the principle of same density--line data are created. After sectional attribution of the resulting polygons a three-dimensional mesh of so-called finite elements is created which can then be used in deformation analysis. This method is exemplified by a project dealing with the simulation of birth mechanics, which is finally aimed at validating the results from radiologic pelvimetry. First analyses show that even under foetal head moulding conditions, being considered as normal, such sensitive structures as the cerebellum, brain stem as well as the ventricles with the plexus chorioidei are to be found within the maximum isobars within a range of 104-140 N(10.6-14.3 kp).

Adult↗
PubMed1992

[Detection of a pheochromocytoma in the urinary bladder wall].

We present the case of a 23-year old female patient with clinical signs and biochemical results of a pheochromocytoma. Abdominal ultrasound gave no hints on localisation. Angiography demonstrated a richly vasculated tumour in the region of the superior urinary bladder. Computed tomography (CT) was able to localise the tumour but could not differentiate the tumour origin in bladder or uterus. The selective venous catheter blood sampling confirmed the localisation of the norepinephrine producing pheochromocytoma in the inferior pelvic region. Intraoperative diagnosis turned out to be an extra-adrenal pheochromocytoma of unknown tumour status in the dorsal bladder wall.

Adult↗
PubMed1992

[MR tomography of the bone marrow in malignant systemic diseases. Diagnosis and therapeutic follow-up control].

This paper presents a short survey of the current status of bone marrow diagnosis in systemic neoplastic disease by means of MR imaging. The different patterns of bone marrow infiltration from lymphomas and leukaemias are presented and the differential diagnoses are discussed. Apart from the primary diagnosis the relevance of conventional MRI and chemical shift imaging for therapy follow up and after-care is discussed.

Bone Marrow↗
PubMed1992

[The treatment of bile duct stenoses using metal mesh endoprostheses (stents)].

Transhepatic biliary drainage is an established therapy for the palliative treatment of biliary stenosis. Long-term biliary drainage may be accomplished by the introduction of an endoprosthesis. Plastic endoprostheses are, however, prone to clogging and dislocation. A new type of endoprosthesis consisting of an expandable metallic mesh has, therefore, been developed. Results in 51 patients using two different types of metallic stents demonstrated that the technical success rate is higher with self-expanding stents than with balloon-expandable stents. Symptoms of obstructive jaundice were effectively palliated in the vast majority of patients (80%). Reobstruction during the first 4 weeks occurred in only 1 patient. Malfunction was related to the inappropriate length of the stent. At follow-up, 25% of patients with malignant biliary strictures developed recurrent jaundice, which was controlled by a single additional placement of a stent or a plastic endoprosthesis. In conclusion, although recurrent biliary stenosis is still a problem, the frequency of reinterventions can be considerably reduced by the use of metallic instead of plastic endoprostheses (20% vs. 45%).

Aged↗
PubMed1992

[Digital image intensifier radiography--what dose for what clinical problem?].

Due to a wide dynamic range it is possible to vary the dose of DIIR for each type of examination according to the required image quality. To define the possible decrease of dose compared to film-screen radiography (speed 200) the dependence of spatial resolution and contrast detectability upon dose was evaluated. We used a Polytron 1000 which was connected to a Siregraph D and an Optilux 57 (Siemens). Acquisition parameters were fixed for different types of examination and tested by imaging anthropomorphic phantoms as well as patients (n = 114). Our results demonstrate that the dose can be reduced by 60% for double-contrast examinations and by 85% for mono-contrast studies. Although DIIR is less suited for chest and skeletal imaging, a 14 cm image intensifier can be used for imaging small lesions. If poor image quality is acceptable (e. g. pelvimetry, sometimes in paediatrics), a maximum reduction of 95% is possible.

Humans↗
PubMed1991

[The radiologic picture of bronchopulmonary aspergillosis].

The increasing incidence of conditions associated with immune suppression, either as part of the illness or as the result of treatment, makes it necessary to investigate the possibility of fungus infections whenever there are broncho-pulmonary changes. In this respect, aspergillus is a common infection which produces more or less typical radiological changes. It often requires a variety of radiological procedures, including the use of CT and nuclear medicine. The latter can be useful in the allergic form of aspergillosis used for ventilation scintigraphy. The possibility of aspergillosis must be brought to the attention of the clinicians by the radiologist, even in cases that are not entirely typical.

Adult↗
PubMed1991

[The value of digital imaging techniques in skeletal imaging].

The clinical value and the imaging characteristics of digital radiography systems (image intensifier (I.I.) radiography: Polytron/Siemens, storage phosphor radiography: PCR/Philipps) in skeletal imaging were compared with film-screen radiography and 100 mm technique. The influence of spatial and contrast resolution, entrance dose and detectability of lytic, osteoblastic and cortical lesions were studied as well as the images of 25 parallel examined patients. Only with the small image intensifier (diameter 14 cm) the quality of 100 mm technique and digital I.I. radiography was equivalent to storage phosphor and film-screen radiography. Storage phosphor radiography seems to be better qualified than I.I. radiography to replace conventional techniques in skeletal imaging.

Bone Neoplasms↗
PubMed1991

[Percutaneous transluminal angioplasty (PTA) of the arteries of the arm in brachial and cerebral ischemia].

35 patients with brachial and/or cerebral ischemia underwent 37 PTA's. Indications for PTA were stenosis (n = 31) or occlusion (n = 1) of the subclavian artery, stenosis of the brachiocephalic trunk (n = 2), stenosis of the axillary artery (n = 2) and stenosis of the brachial artery (n = 1). 23 patients demonstrated a subclavian steal phenomenon. However, the minority of patients (n = 10) presented with neurologic symptoms, which could be provoked by brachial exercise in only 3 patients. 7 of the 10 patients with cerebral ischaemia demonstrated additional significant stenosis of the extracranial arteries. The technical success rate for PTA was 89.2%. Two patients showed relapse of the stenosis. The clinical success rate regarding brachial ischaemia was 94.4% (follow-up: 6-37 months). Neurologic symptoms disappeared after treatment in 72.7%. Minor complications without clinical sequelae occurred in 8.6%.

Adult↗
PubMed1991

[The Kodak AMBER imaging system--a new approach to lung imaging].

The exposure range of X-ray films is often too small for objects with large absorption differences. This holds true also for wide latitude films. The large absorption differences can be equalized with the Kodak AMBER Imaging System by means of local exposure control. The AMBER System is a variation of the slit technique, where the narrowly collimated beam is divided into 21 beam segments the intensity of which is controlled in relation to the absorption in the object. This results in radiographs which are well exposed in the lung parenchyma and the mediastinum. An AMBER System has been routinely used for chest radiography in the Klinikum Mannheim since April 1990. The radiographs with the AMBER-Systems show an improved image quality especially in the mediastinum and the thorax wall resulting in a gain in diagnostic information.

Humans↗