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Biomedical subjects

H Schüller

Publications and source records attributed to H Schüller.

At least 37 records · Page 2Linked to original sources
PubMed1998

Fixation monitoring during radiation therapy for subfoveal neovascularization.

PURPOSE: The aim of the study was to determine movement of the fovea during each irradiation session by monitoring movement of the cornea. Knowing the extent of foveal deviation permits minimization of the field size. METHODS: (1) Eye movement was monitored in 10 patients during irradiation. A TV camera with an attached fixation light was installed 3 cm away from the cornea of the treated eye. The fixation light was positioned at a 10 degrees angle to the TV camera on the opposite side of the gantry, resulting in a 90 degrees angle between the optical axis of the eye and the irradiation beam. (2) The relationship between movement of the anterior and posterior eye segments of 10 volunteers was examined using a scanning laser ophthalmoscope (SLO). Volunteers were asked to fix their gaze on positioning lights installed in the SLO. Gaze movements of the anterior and posterior eye segments were recorded simultaneously. RESULTS: (1) The patients' ability to retain fixation differed interindividually. The median corneal deviation during 10 irradiation sessions was 1 mm mediolaterally and 0.7 mm craniocaudally. (2) Deviation of the fovea could be determined by monitoring deviation of the cornea. Measured by SLO, the correlation between movements of the anterior and posterior eye segments was 1:0.9 horizontally and 1:1.5 vertically. CONCLUSION: (1) Irradiation field size can be reduced, depending on the patient's fixation stability. (2) If monitoring reveals a foveal deviation beyond the 95% isodose, irradiation can be interrupted.

Choroidal Neovascularization↗
PubMed1998

[Radiation exposure of radiation-sensitive risk organs--ocular lens, parotid gland, thyroid gland--in dacryocystography and therapy].

PURPOSE: Evaluation of radiation dose to the radiosensitive head and neck organs and tissues-ocular lens, parotid and thyroid glands--during dacryocystography and fluoroscopy--guided dacryocystoplasty (DCP). METHOD: Radiation dose was determined in an Alderson Rando phantom and in 13 patients. Radiation dose was measured directly using Ca-F2-thermoluminescent dosimetry crystals (TLD) which were placed on each eyelid, parotid gland and thyroid gland. RESULTS: The mean radiation dose to the lens placed next to the path of radiation was 6.58 mGy in the Alderson-Rando phantom and 5.43 mGy in patients during DCP. The mean radiation dose to the contralateral lens was 1.37 mGy and 1.7 mGy to the parotid gland placed next to the x-ray tube. Radiation dose to the thyroid gland was max. 0.4 mGy during DCP. CONCLUSION: Radiation dose to the ocular lens, parotid gland and thyroid gland during fluoroscopy-guided DCP was 25 times higher than during diagnostic dacryocystography. The radiation dose to radiosensitive head and neck organs and tissues during fluoroscopy-guided DCP is much below the threshold dose for ocular lens cataract.

Dacryocystitis↗
PubMed1998

[TIPSS: technical and clinical results after 4 years].

PURPOSE: Retrospective analysis of the technical and clinical results after transjugular portosystemic stent shunt (TIPSS) procedure. METHOD: Between 1992 and 1996 we tried to establish a TIPSS in 90 patients. The indications were: recurrent variceal haemorrhage (n = 74), refractory ascites (n = 12), hepatorenal syndrome (HRS) (n = 4). Due to advanced liver cirrhosis 16 patients suffered of severe renal dysfunction (HRS). 57 patients had ascites. RESULTS: TIPSS implantation was technically successful in 96.7% (1992-1994: 5.1%, 1995-1996: 100%) of the patients. Complications occurred in 14.9% (1992-1994: 25.6%, 1995-1996: 6.3%). TIPSS-associated mortality was 2.3% (1992-1994: 5.1%, 1995-1996: 0%). 76.1% of the patients required reinterventions. 85.3% of reinterventions were necessary in the first year after TIPSS placement. The survival rate without reintervention was 28%, 21% and 9% for Child A, B, and C patients, respectively. Recurrent variceal haemorrhage occurred in 12.7%. De novo hepatic encephalopathy developed in 13.8%. Ascites improved in 79.2% and renal function in 75% of the patients. CONCLUSION: TIPSS is an effective method to treat recurrent variceal haemorrhage, refractory ascites and HRS. Complication and mortality rate depend on the investigator's experience and on the technique used.

Adult↗
PubMed1998

[Quantitative evaluation of the suitability of magnetic resonance sequences for the detection of spinal bone marrow metastases of solid tumors].

AIM: To compare MR sequences for the examination of the bone marrow of the spine in the detection of skeletal metastases. METHODS: 20 standardised prospective studies of the cervical, thoracic or lumbar spine in patients with known skeletal metastases were evaluated quantitatively. Studies included T1w SE with and without intravenous contrast medium (CM) administration of Gd-DTPA, T2w TSE with and without frequence selective fat saturation (SPIR), opposed phase gradient echo (opGE) with and without intravenous CM administration of Gd-DTPA and T1w SE CM SPIR sequences. The quantitative parameters signal/noise ratio (SNR), contrast/noise ratio (CNR) and contrast were evaluated. RESULTS: OpGE with contrast showed the best results in SNR, CNR and C. Results were statistically significant. Good SNR and C also was found for T1w SE native. SPIR and T2w sequences were less sensitive. CONCLUSION: OpGE sequences are recommended for the detection of skeletal metastases of the spine.

Bone Marrow Neoplasms↗
PubMed1998

Automatic adjustment of pacemaker stimulation output correlated with continuously monitored capture thresholds: a multicenter study. European Microny Study Group.

Pacing threshold is affected by many factors. A pacing system able to confirm capture at each beat and automatically adjust its output close to the actual pacing threshold is highly desirable. This study evaluates the safety and efficacy of the Autocapture function of the Pacesetter Microny SR+. One hundred thirteen patients were recruited from 16 centers in 7 European countries and followed up for 1 year. All pacemakers were implanted with Pacesetter's low polarization, bipolar leads. The key feature of Autocapture is the immediate delivery of a 4.5 V safety backup pulse 62.5 ms after any ineffective ongoing low output pulse. Holter recordings confirmed total reliability of this feature without any exit block. The measured evoked response (ER) signal was stable over time. Acute and chronic pacing thresholds measured by VARIO and Autocapture tests correlated (r > 0.79) over the period of the study. The incidence of backup pulses was 1.1% during pacing. With Autocapture programmed ON, the overall total current consumption was 4.1 microA for VVI and 5.0 microA for VVIR pacing. This study proved that the Autocapture safely and reliably regulates the pacemaker's output according to the prevailing threshold thus providing maximum patient safety and prolonging service life.

Aged↗
PubMed1998

A software sensor using neural networks for detection of patient workload.

The morphology of intracardiac electrograms (IEGMs) was used for pacemaker patient workload estimation. The body posture also was studied as another characteristic. The IEGMs were obtained and recorded via temporary transcutaneous leads connected to the implanted pacemaker. IEGMs were recorded during exercise and at rest. Recordings at rest were performed in different body positions. The morphology was analyzed visually in order to observe changes due to workload and posture. The recordings were digitized and processed by a computer-simulated neural network. The network was used as an automatic IEGM classifier based on the morphology. Our results show that the morphology of the IEGM may be used as an indicator of patient workload and body posture. The necessary information is found mainly in the ST segment. We conclude that neural networks seem to be useful in an active cardiac device.

Aged↗
PubMed1997

[The diagnosis of intra-abdominal hemorrhages with CO2 as the contrast medium].

PURPOSE: Evaluation of carbon dioxide (CO2) as contrast medium for detection of intraabdominal haemorrhage. METHOD: We performed in 5 patients 7 DSA examinations (one with upper and three with lower gastrointestinal bleeding, one traumatic spleen rupture) using an iodinated contrast-medium and CO2 for the localisation of haemorrhage. RESULTS: With iodinated contrast medium it was possible to localise the haemorrhage in three of 5 patients. With CO2 the localisation was possible in all cases. There were no side effects. CONCLUSION: CO2 is useful for detection of intraabdominal bleeding. Even in cases with negative angiographic results with iodinated contrast medium, CO2 may enable localisation of the bleeding vessel. Because of this, we use CO2 and iodinated contrast media in all cases of intraabdominal haemorrhage. Further studies are required.

Angiography, Digital Subtraction↗
PubMed1997

[Carbon dioxide (CO2) as contrast medium for the new installation and follow-up of a TIPS].

PURPOSE: To determine the efficacy of CO2 as negative contrast medium compared with iodinated contrast medium in creation and control of TIPS. MATERIAL AND METHODS: CO2 was used during TIPS procedures in 33 patients. In 21 patients a wedged hepatic venography was obtained for planning the shunt tract. Additional TIPS-control DSA was performed in 42 cases by direct portal venography to verify the TIPS function and patency. In all cases CO2 gas was used in addition to iodinated contrast medium. RESULTS: CO2 produced excellent wedged hepatic venographies in all patients. Visualisation of the portal veins and collaterals was superior to iodinated contrast medium. The TIPS-control DSA performed with CO2 were comparable to those performed with iodinated contrast medium. Complications were not observed in our study. CONCLUSION: CO2 is an effective contrast medium for TIPS procedures. In particular the visualisation of portal veins performed by CO2-wedged hepatic venography is superior to iodinated contrast medium.

Adult↗
PubMed1997

[MRI dacryocystography after applying gadolinium-containing eyedrops].

PURPOSE: To determine the efficacy of MRI for the lacrimal drainage system after conjunctival application of gadolinium-DTPA solution. MATERIAL AND METHODS: MRI dacryocystography of 32 nasolacrimal duct systems was performed in 16 patients additional to digital subtraction dacryocystography. The gadolinium solution was prepared by diluting the commercially available gadolinium-DTPA (Magnevist, Schering AG, Berlin) 1:10 in sterile saline solution. 3 x 2 drops of this contrast medium were instilled bilaterally immediately before MRI scanning. RESULTS: MRI dacryocystography provided detailed information on the nasolacrimal duct system in all 32 cases. In 16 cases localisation and functional degree of nasolacrimal duct obstruction or stenosis was determined reliably. In 15 cases normal nasolacrimal duct system showed no contrast enhancement. In one case stenosis of the canaliculus was observed. CONCLUSION: MRI dacryocystography provides detailed morphological soft tissue information of the lacrimal drainage system. Local conjunctival application of gadolinium solution allows functional tests of the lacrimal duct system in patients suffering from epiphora.

Adult↗
PubMed1997

[CO2 cholangiography].

PURPOSE: Evaluation of the benefit of carbon dioxide (CO2) as contrast medium to reduce intraductal manipulations in biliary drainage. METHOD: In 8 patients with biliary occlusion demonstrated by cholangiography with iodinated contrast medium, percutaneous CO2 cholangiography was performed by manual injection of 30-50 ml CO2 using the same approach. Capability of CO2 to pass the obstruction and delineate distal parts of the common bile duct was evaluated. RESULTS: In 5 of 8 patients CO2 visualised additional segments of the occluded bile duct. In 4 patients the poststenotic bile duct was demonstrated with CO2. In one patient 2 cm of the obstructed duct segment was visualised. The intrahepatic duct system could not be examined sufficiently by CO2 administration. CONCLUSION: Because of its low viscosity, CO2 is a useful contrast medium to visualise the extrahepatic biliary system before performing an external-internal biliary drainage in biliary obstruction. Unnecessary intraductal manipulations may be reduced.

Carbon Dioxide↗
PubMed1997

[MR relaxation time measurements with and without selective fat suppression (SPIR) in endocrine orbitopathy].

PURPOSE: To determine the value and utility of relaxation time measurements with magnetic resonance (MR) imaging in patients with Graves' ophthalmopathy (G.O.). MATERIALS AND METHODS: 20 orbits were studied in control subjects and 58 orbits in patients with G.O. T2 relaxation times of extraocular muscles and retrobulbar fat tissue were calculated. The thickness of the eye muscles was correlated with the calculated T2 times. 18 orbits were measured before and after retro-orbital radiation therapy. RESULTS: Upper limits of determined normal T2 values were 60 ms in extraocular eye muscles and 40 ms in retrobulbar fat tissue. 89% (17/19) of the patients with G.O. had prolonged T2 times in extraocular eye muscles. The retrobulbar fat tissue in 5 of 38 orbits revealed minimal edema with the use of fat saturated sequences. T2 relaxation times decreased significantly (p < 10(-4)) after 10 Gy radiation therapy. No correlation was found between enlargement and T2 relaxation times in extraocular eye muscles (r = 0.44 in patients before radiation therapy). CONCLUSION: In patients with G.O. the determination of the enlargement of extraocular eye muscles in computed tomography is not a sufficient parameter for an antiinflammatory therapy, since CT cannot visualise eye muscle edema. T2 relaxation time measurements with MR imaging allow differentiation between edematous and fibrotic changes. This is the diagnostic method of choice in patients with Graves' ophthalmopathy.

Adipose Tissue↗
PubMed1997

Breast preservation versus mastectomy--recurrence and survival rates of primary breast cancer patients treated at the UFK Bonn.

The aim of this retrospective long-term analysis was to evaluate the approach of breast conservation in the light of the results obtained, on the basis of mastectomy, in patients with early breast carcinoma. Additionally, the effect of internal mammary and supraclavicular radiotherapy was analyzed. Therefore, local-regional recurrence (LRR) and survival rates were examined in 411 patients with T1 and T2 stages who had undergone either breast-preserving surgery with radiation or mastectomy. Individual risk factors such as nodal status, lymphangiosis carcinomatosa and age of the patients were evaluated, too. The rate of local-regional recurrence in patients who were treated by mastectomy and conservative surgery was 9.2% and 11.0%, respectively, with relapse happening earlier in the latter group (median of 16 vs. 24 months). Survival rates, however, were not different in the two groups. Tumour stage and nodal status had no influence on the local-regional recurrence rate in either group. In connection with lymphangiosis carcinomatosa, however, the rate increased to 14.5% (mastectomy) and 19.0% (breast-preserving surgery), respectively. Patients < or = 40 years had an even higher risk of LRR, with 20.6% when they underwent mastectomy and 30.8% following breast conservation. Internal mammary and supraclavicular radiotherapy had no positive effect on the survival rates, neither in the mastectomy nor in the breast conservation group. As a conclusion, in more than 60% of all T1 stages. and more than 50% of all T2 stages, the therapeutic concept of breast preservation seems to be justified.

Adult↗
PubMed1997

[Percutaneous radiotherapy of bone metastases].

Bone metastases causing pain syndromes and imminent pathologic fractures are among the main reasons for radiotherapy in patients suffering from malignant tumors. The indication is much influenced by the radiologic findings. Surgical methods are to be chosen in the first place in cases of pathologic fractures or patients with a high risk of such fractures. Different authors recommend various therapeutic regimens. Effective pain control can be achieved with one single dose of radiation. Doses of 6 to 40 Gy applied in one to 19 days are also efficient. Side effects, especially nausea and vomiting occur in 25% of cases; this number rises to 50% in cases of half body irradiation. Visible changes of bone mineral density may be noticed about 6 weeks after termination of radiotherapy. About 70% of osteolytic metastases show progressive sclerosis whereas osteosclerotic lesions may show both increase or decline of bone mass. In spite many years of experience the optimal strategy for radiation therapy of bone metastasis has not been defined; further studies are needed.

Bone Density↗
PubMed1996

[Computerized tomography of the alveolar process].

In addition to the conventional radiological methods used in odontology, computed tomography (CT) provides superposition-free images of the mandible and maxilla. Its value has been proved not only in cases of malignancy but also in many other problems. If an examination is performed with a slice thickness of less than 1.5 mm, the form and position of retained teeth in the alveolar bone, as well as subsequent lesions of neighboring permanent teeth, can be visualized so that early treatment can be planned. If the parodontal space of a retained tooth is visible, orthodontic intervention is possible. Precise assessment of horizontal or vertical bone loss is essential in inflammatory dental diseases. The morphology and extent of benign cystic lesions are also shown by CT. With CT surgical strategy of an intended implant therapy can take into account the remaining bone substance and the exact position of nerves and foramina. If such therapy is possible, the location, form and number of implants are easily defined.

Alveolar Bone Loss↗
PubMed1996

[Early pulmonary changes caused by amiodarone].

Confluent infiltrates and interstitial condensates with (sub)segmentary spreading are typical radiological findings in amiodarone pneumopathy. A case is presented where daily amounts of 200-600 mg and a total of 18.3 g amiodarone led to alveolitis with fibrosis within 4 weeks, which is uncommon in the early stage.

Aged↗
PubMed1995

[Incisor roots in the mandibular symphysis in the computed tomogram and in the lateral teleradiogram].

On the basis of lateral cephalograms and computer tomograms (CT) the position of the incisor roots and the bone structure surrounding them were studied. Nine patients each had an axial CT of the mandibular symphysis area and, in addition, 6 of these patients had lateral cephalograms. In order to compare both images, we defined a classification scheme as follows: Class 1 = the incisor roots are projected into the midst of the oral corticalis of the symphysis; class 2 = the roots are in contact with the oral corticalis; class 3 = the incisor roots are at a distance to the oral corticalis. The results from the 2 types of visualization were then compared. When looking at the bone structures surrounding the incisor roots, the lateral cephalograms failed to yield an exact differentiation. Such details can be best examined in the axial CT layers, because in the lateral cephalogram the 4 incisor roots are over projected to 1 root. The space for movement of the incisors is narrow. The root of each and every patient showed a different position in oro-buccal direction. This fact must be taken into consideration in clinical practice, especially when employing fixed appliances with 3-dimensional root control.

Evaluation Studies as Topic↗
PubMed1994

Pacing for sinus node disease: a therapeutic rationale.

Symptomatic sinus node disease is a common indication for permanent pacemaker implantation. Single-chamber ventricular (VVI) pacing, single-chamber atrial (AAI) stimulation, and dual-chamber (DDD or DDI) systems are used to a varying extent at different implanting centers. Hemodynamic and clinical studies relevant to the choice of pacing mode in these patients are reviewed. The data currently available strongly support the use of pacing systems providing atrial stimulation. The choice between single-chamber atrial or dual-chamber pacing can be based on the relative importance assigned to a number of factors: Hemodynamic aspects, the risk of ventricular lead problems, cost, and complexity aspects favor AAI pacing, whereas patients with a substantial risk of developing atrioventricular block should receive a DDD or DDI unit.

Arrhythmia, Sinus↗